L. Orsini

Data acquisition systems are mission-critical components in high-energy physics experiments. They are embedded in an environment of custom electronics, and are frequently characterized by high performance requirements. With the advent of powerful mainstream computing platforms and affordable high-speed networking equipment, system cost and time to completion can be significantly reduced. There still exists a considerable effort in custom software developments to build these systems and make them running efficiently. Therefore we strive for a software architecture flexible and robust enough to be usable in different system configurations and deployment cases. The software should cover the largest possible application domain and provide a practical balance between efficiency and flexibility. This article pinpoints the requirements imposed on such an on-line software infrastructure and sheds light on a viable design approach. As such, this article aims at laying out the foundations for a broader understanding of the importance for fostering a homogeneous architecture for high-energy physics data acquisition.

The CMS data acquisition system is made of two major subsystems: event building and event filter. The presented paper describes the architecture and design of the software that processes the data flow in the currently operating experiment. The central DAQ system relies on industry standard networks and processing equipment. Adopting a single software infrastructure in all subsystems of the experiment imposes, however, a number of different requirements. High efficiency and configuration flexibility are among the most important ones. The XDAQ software infrastructure has matured over an eight years development and testing period and has shown to be able to cope well with the requirements of the CMS experiment.

The CMS data acquisition (DAQ) is implemented as a service-oriented architecture where DAQ applications, as well as general applications such as monitoring and error reporting, are run as self-contained services. The task of deployment and operation of services is achieved by using several heterogeneous facilities, custom configuration data and scripts in several languages. In this work, we restructure the existing system into a homogeneous, scalable cloud architecture adopting a uniform paradigm, where all applications are orchestrated in a uniform environment with standardized facilities. In this new paradigm DAQ applications are organized as groups of containers and the required software is packaged into container images. Automation of all aspects of coordinating and managing containers is provided by the Kubernetes environment, where a set of physical and virtual machines is unified in a single pool of compute resources. We demonstrate that a container-based cloud architecture provides an acrossthe-board solution that can be applied for DAQ in CMS. We show strengths and advantages of running DAQ applications in a container infrastructure as compared to a traditional application model.

The Online Monitoring System (OMS) at the Compact Muon Solenoid experiment (CMS) at CERN aggregates and integrates different sources of information into a central place and allows users to view, compare and correlate information. It displays real-time and historical information. The tool is heavily used by run coordinators, trigger experts and shift crews, to ensure the quality and efficiency of data taking. It provides aggregated information for many use cases including data certification. OMS is the successor of Web Based Monitoring (WBM), which was in use during Run 1 and Run 2 of the LHC. WBM started as a small tool and grew substantially over the years so that maintenance became challenging. OMS was developed from scratch following several design ideas: to strictly separate the presentation layer from the data aggregation layer, to use a well-defined standard for the communication between presentation layer and aggregation layer, and to employ widely used frameworks from outside the HEP community. A report on the experience from the operation of OMS for the first year of data taking of Run 3 in 2022 is presented.

The data acquisition (DAQ) of the Compact Muon Solenoid (CMS) experiment at CERN, collects data for events accepted by the Level-1 Trigger from the different detector systems and assembles them in an event builder prior to making them available for further selection in the High Level Trigger, and finally storing the selected events for offline analysis. In addition to the central DAQ providing global acquisition functionality, several separate, so-called “MiniDAQ” setups allow operating independent data acquisition runs using an arbitrary subset of the CMS subdetectors. During Run 2 of the LHC, MiniDAQ setups were running their event builder and High Level Trigger applications on dedicated resources, separate from those used for the central DAQ. This cleanly separated MiniDAQ setups from the central DAQ system, but also meant limited throughput and a fixed number of possible MiniDAQ setups. In Run 3, MiniDAQ-3 setups share production resources with the new central DAQ system, allowing each setup to operate at the maximum Level-1 rate thanks to the reuse of the resources and network bandwidth. Configuration management tools had to be significantly extended to support the synchronization of the DAQ configurations needed for the various setups. We report on the new configuration management features and on the first year of operational experience with the new MiniDAQ-3 system.

The Compact Muon Solenoid (CMS) experiment at CERN incorporates one of the highest throughput data acquisition systems in the world and is expected to increase its throughput by more than a factor of ten for High-Luminosity phase of Large Hadron Collider (HL-LHC). To achieve this goal, the system will be upgraded in most of its components. Among them, the event builder software, in charge of assembling all the data read out from the different sub-detectors, is planned to be modified from a single event builder to an orbit builder that assembles multiple events at the same time. The throughput of the event builder will be increased from the current 1.6 Tb/s to 51 Tb/s for the HL-LHC orbit builder. This paper presents preliminary network transfer studies in preparation for the upgrade. The key conceptual characteristics are discussed, concerning differences between the CMS event builder in Run 3 and the CMS Orbit Builder for the HL-LHC. For the feasibility studies, a pipestream benchmark, mimicking event-builder-like traffic has been developed. Preliminary performance tests and results are discussed.

Abstract This paper describes recent progress on the design of the DAQ and Timing Hub, or DTH, an ATCA (Advanced Telecommunications Computing Architecture) hub board intended for the phase-2 upgrade of the CMS experiment. Prototyping was originally divided into multiple feature lines, spanning all different aspects of the DTH functionality. The second DTH prototype merges all R&D and prototyping lines into a single board, which is intended to be the production candidate. Emphasis is on the process and experience in going from the first to the second DTH prototype, which included a change of the chosen FPGA as well as the integration of a commercial networking solution.

Interleukin-8 is a cytokine produced by mononuclear cells that is involved in polymorphonuclear neutrophil leukocyte (PMN) recruitment and activation. Several studies have previously demonstrated a leukocyte activation during hypercholesterolemia and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been found to play a role in the prevention of atherothrombotic disease. The purpose of this study was to determine interleukin-8 (IL-8) mRNA expression and ex vivo production from peripheral blood mononuclear cells (PBMCs) and IL-8-dependent PMN activation of hypercholesterolemic (HC) patients with respect to normocholesterolemic (NC) subjects. Using Northern blot analysis, we found a four- and threefold increase in the amount of IL-8 transcript in PBMC from HC patients, in unstimulated and LPS stimulated cultures, respectively. A specific immunoassay showed a correspondingly significant increase of IL-8 immunoactivity in the conditioned medium of PBMC from HC subjects as compared with controls (unstimulated PBMC: 15 +/- 4 vs. 4.2 +/- 3 ng/ml; P < 0.0001; LPS stimulated PBMC: 65.3 +/- 8 vs. 36.6 +/- 9 ng/ml; P < 0.0001). PMN of HC patients stimulated with IL-8 showed a reduced elastase release with respect to NC subjects before physiological granule release after f-Met-Leu-Phe (fMLP) treatment. These results indicate an upregulation of the IL-8 system in dyslipidemic patients and provide evidence for ongoing in vivo IL-8-dependent PMN activation during hypercholesterolemia.

The data-acquisition system of the CMS experiment at the LHC performs the read-out and assembly of events accepted by the first level hardware trigger. Assembled events are made available to the high-level trigger which selects interesting events for offline storage and analysis. The system is designed to handle a maximum input rate of 100 kHz and an aggregated throughput of 100GB/s originating from approximately 500 sources. An overview of the architecture and design of the hardware and software of the DAQ system is given. We discuss the performance and operational experience from the first months of LHC physics data taking.

The data acquisition (DAQ) system of the CMS experiment at the CERN Large Hadron Collider assembles events at a rate of 100 kHz, transporting event data at an aggregate throughput of 100 GB/s to the high level trigger (HLT) farm. The HLT farm selects interesting events for storage and offline analysis at a rate of around 1 kHz. The DAQ system has been redesigned during the accelerator shutdown in 2013/14. The motivation is twofold: Firstly, the current compute nodes, networking, and storage infrastructure will have reached the end of their lifetime by the time the LHC restarts. Secondly, in order to handle higher LHC luminosities and event pileup, a number of sub-detectors will be upgraded, increasing the number of readout channels and replacing the off-detector readout electronics with a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu {\hbox {TCA}}$</tex></formula> implementation. The new DAQ architecture will take advantage of the latest developments in the computing industry. For data concentration, 10/40 Gb/s Ethernet technologies will be used, as well as an implementation of a reduced TCP/IP in FPGA for a reliable transport between custom electronics and commercial computing hardware. A Clos network based on 56 Gb/s FDR Infiniband has been chosen for the event builder with a throughput of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim 4~\hbox{Tb/s}$</tex> </formula> . The HLT processing is entirely file based. This allows the DAQ and HLT systems to be independent, and to use the HLT software in the same way as for the offline processing. The fully built events are sent to the HLT with 1/10/40 Gb/s Ethernet via network file systems. Hierarchical collection of HLT accepted events and monitoring meta-data are stored into a global file system. This paper presents the requirements, technical choices, and performance of the new system.

The CMS data acquisition system is designed to build and filter events originating from 476 detector data sources at a maximum trigger rate of 100 kHz. Different architectures and switch technologies have been evaluated to accomplish this purpose. Events will be built in two stages: the first stage will be a set of event builders called front-end driver (FED) builders. These will be based on Myrinet technology and will pre-assemble groups of about eight data sources. The second stage will be a set of event builders called readout builders. These will perform the building of full events. A single readout builder will build events from about 60 sources of 16 kB fragments at a rate of 12.5 kHz. In this paper, we present the design of a readout builder based on TCP/IP over Gigabit Ethernet and the refinement that was required to achieve the design throughput. This refinement includes architecture of the readout builder, the setup of TCP/IP, and hardware selection.

The DAQ system of the CMS experiment at CERN collects data from more than 600 custom detector Front-End Drivers (FEDs). During 2013 and 2014 the CMS DAQ system will undergo a major upgrade to address the obsolescence of current hardware and the requirements posed by the upgrade of the LHC accelerator and various detector components. For a loss-less data collection from the FEDs a new FPGA based card implementing the TCP/IP protocol suite over 10Gbps Ethernet has been developed. To limit the TCP hardware implementation complexity the DAQ group developed a simplified and unidirectional but RFC 793 compliant version of the TCP protocol. This allows to use a PC with the standard Linux TCP/IP stack as a receiver. We present the challenges and protocol modifications made to TCP in order to simplify its FPGA implementation. We also describe the interaction between the simplified TCP and Linux TCP/IP stack including the performance measurements.

For the upgrade of the DAQ of the CMS experiment in 2013/2014 an interface between the custom detector Front End Drivers (FEDs) and the new DAQ eventbuilder network has to be designed. For a loss-less data collection from more then 600 FEDs a new FPGA based card implementing the TCP/IP protocol suite over 10Gbps Ethernet has been developed. We present the hardware challenges and protocol modifications made to TCP in order to simplify its FPGA implementation together with a set of performance measurements which were carried out with the current prototype.

The Pixel Luminosity Telescope is a silicon pixel detector dedicated to luminosity measurement at the CMS experiment at the LHC. It is located approximately 1.75 m from the interaction point and arranged into 16 "telescopes", with eight telescopes installed around the beam pipe at either end of the detector and each telescope composed of three individual silicon sensor planes. The per-bunch instantaneous luminosity is measured by counting events where all three planes in the telescope register a hit, using a special readout at the full LHC bunch-crossing rate of 40 MHz. The full pixel information is read out at a lower rate and can be used to determine calibrations, corrections, and systematic uncertainties for the online and offline measurements. This paper details the commissioning, operational history, and performance of the detector during Run 2 (2015-18) of the LHC, as well as preparations for Run 3, which will begin in 2022.

Abstract The control of cavities sealing has been a challenging problem since early gas turbine development stages and several aspects regarding the flow physics and the modeling of rim seal flows, especially in terms of unsteady phenomena, still represent an open question. Fundamental test cases have been extensively used in the open literature to characterize the level of ingestion by varying the main flow parameters and the geometrical features. In most of them, the seal effectiveness is measured by using taps connected to a gas analyzer used to sample the concentration on the stator surface of a reference foreign gas (generally CO2) used to seed the purge flow. Consequently, the results are usually single-point measurements, and unsteady effects are inevitably neglected. Moreover, the intrusiveness of the approach must be carefully checked, and the application on the rotor side demands for complex slip-rings or telemetry. To overcome these limitations, the current work presents the application of the pressure-sensitive paint (PSP) technique to the study of hot gas ingestion phenomena on a single-stage rotating cold rig. By using an oxygen-free gas such as N2 as purge flow, the PSP was used to measure the partial pressure of oxygen at the wall through the wide optical accesses present in the rig. Then, the collected 2D distributions of pressure were related to the seal effectiveness inside the wheel space. The proposed methodology was first validated through a comparison with the data obtained from standard gas sampling and then applied as main experimental technique to characterize the seal ingestion. The analysis of the results highlighted the capabilities of the PSP technique to fast collect data on both stator and rotor sides, including the tip of the seal tooth where nonuniform efficiency distributions in the circumferential direction have been detected.

The Compact Muon Solenoid (CMS) experiment operating at the CERN (European Laboratory for Nuclear Physics) Large Hadron Collider (LHC) is in the process of upgrading several of its detector systems. Adding more individual detector components brings the need to test and commission those components separately from existing ones so as not to compromise physics data-taking. The CMS Trigger, Timing and Control (TTC) system had reached its limits in terms of the number of separate elements (partitions) that could be supported. A new Timing and Control Distribution System (TCDS) has been designed, built and commissioned in order to overcome this limit. It also brings additional functionality to facilitate parallel commissioning of new detector elements. The new TCDS system and its components will be described and results from the first operational experience with the TCDS in CMS will be shown.

The CMS experiment at the LHC at CERN will start taking data in 2008. To configure, control and monitor the experiment during data-taking the Run Control system was developed. This paper describes the architecture and the technology used to implement the Run Control system, as well as the deployment and commissioning strategy of this important component of the online software for the CMS experiment.

The Data Acquisition System of the Compact Muon Solenoid experiment at the Large Hadron Collider reads out event fragments of an average size of 2 kB from around 650 detector front-ends at a rate of up to 100 kHz. The first stage of event-building is performed by the Super-Fragment Builder employing custom-built electronics and a Myrinet optical network. It reduces the number of fragments by one order of magnitude, thereby greatly decreasing the requirements for the subsequent event-assembly stage. Back-pressure from the down-stream event-processing or variations in the size and rate of events may give rise to buffer overflows in the subdetector's front-end electronics, which would result in data corruption and would require a time-consuming re-sync procedure to recover. The Trigger-Throttling System protects against these buffer overflows. It provides fast feedback from any of the subdetector front-ends to the trigger so that the trigger can be throttled before buffers overflow. This paper reports on new performance measurements and on the recent successful integration of a scaled-down setup of the described system with the trigger and with front-ends of all major subdetectors. The on-going commissioning of the full-scale system is discussed.

The CMS data acquisition system comprises O(20000) interdependent services that need to be monitored in near real-time. The ability to monitor a large number of distributed applications accurately and effectively is of paramount importance for robust operations. Application monitoring entails the collection of a large number of simple and composed values made available by the software components and hardware devices. A key aspect is that detection of deviations from a specified behaviour is supported in a timely manner, which is a prerequisite in order to take corrective actions efficiently. Given the size and time constraints of the CMS data acquisition system, efficient application monitoring is an interesting research problem. We propose an approach that uses the emerging paradigm of Web-service based eventing systems in combination with hierarchical data collection and load balancing. Scalability and efficiency are achieved by a decentralized architecture, splitting up data collections into regions of collections. An implementation following this scheme is deployed as the monitoring infrastructure of the CMS experiment at the Large Hadron Collider. All services in this distributed data acquisition system are providing standard web service interfaces via XML, SOAP and HTTP [15,22]. Continuing on this path we adopted WS-* standards implementing a monitoring system layered on top of the W3C standards stack. We designed a load-balanced publisher/subscriber system with the ability to include high-speed protocols [10,12] for efficient data transmission [11,13,14] and serving data in multiple data formats.

The CMS event builder assembles events accepted by the first level trigger and makes them available to the high-level trigger. The event builder needs to handle a maximum input rate of 100 kHz and an aggregated throughput of 100 GB/s originating from approximately 500 sources. This paper presents the chosen hardware and software architecture. The system consists of 2 stages: an initial pre-assembly reducing the number of fragments by one order of magnitude and a final assembly by several independent readout builder (RU-builder) slices. The RU-builder is based on 3 separate services: the buffering of event fragments during the assembly, the event assembly, and the data flow manager. A further component is responsible for handling events accepted by the high-level trigger: the storage manager (SM) temporarily stores the events on disk at a peak rate of 2 GB/s until they are permanently archived offline. In addition, events and data-quality histograms are served by the SM to online monitoring clients. We discuss the operational experience from the first months of reading out cosmic ray data with the complete CMS detector.

The CMS experiment at the LHC features a two-level trigger system. Events accepted by the first level trigger, at a maximum rate of 100 kHz, are read out by the Data Acquisition system (DAQ), and subsequently assembled in memory in a farm of computers running a software high-level trigger (HLT), which selects interesting events for offline storage and analysis at a rate of order few hundred Hz. The HLT algorithms consist of sequences of offline-style reconstruction and filtering modules, executed on a farm of 0(10000) CPU cores built from commodity hardware. Experience from the operation of the HLT system in the collider run 2010/2011 is reported. The current architecture of the CMS HLT, its integration with the CMS reconstruction framework and the CMS DAQ, are discussed in the light of future development. The possible short- and medium-term evolution of the HLT software infrastructure to support extensions of the HLT computing power, and to address remaining performance and maintenance issues, are discussed.

As part of the CMS upgrade during CERN's shutdown period (LS1), the CMS data acquisition system is incorporating Infiniband FDR technology to boost event-building performance for operation from 2015 onwards.Infiniband promises to provide substantial increase in data transmission speeds compared to the older 1GE network used during the 2009-2013 LHC run.Several options exist to end user developers when choosing a foundation for software upgrades, including the uDAPL (DAT Collaborative) and Infiniband verbs libraries (OFED).Due to advances in technology, the CMS data acquisition system will be able to achieve the required throughput of 100 kHz with increased event sizes while downsizing the number of nodes by using a combination of 10GE, 40GE and 56 Gb Infiniband FDR.This paper presents the analysis and results of a comparison between GE and Infiniband solutions as well as a look at how they integrate into an event building architecture, while preserving the scalability, efficiency and deterministic latency expected in a high end data acquisition network.

The DAQ and Timing Hub is an ATCA hub board designed for the Phase-2 upgrade of the CMS experiment.In addition to providing high-speed Ethernet connectivity to all back-end boards, it forms the bridge between the sub-detector electronics and the central DAQ, timing, and trigger control systems.One important requirement is the distribution of several high-precision, phasestable, and LHC-synchronous clock signals for use by the timing detectors.The current paper presents first measurements performed on the initial prototype, with a focus on clock quality.It is demonstrated that the current design provides adequate clock quality to satisfy the requirements of the Phase-2 CMS timing detectors.

The High Luminosity LHC (HL-LHC) will start operating in 2027 after the third Long Shutdown (LS3), and is designed to provide an ultimate instantaneous luminosity of 7:5 × 10 34 cm −2 s −1 , at the price of extreme pileup of up to 200 interactions per crossing. The number of overlapping interactions in HL-LHC collisions, their density, and the resulting intense radiation environment, warrant an almost complete upgrade of the CMS detector. The upgraded CMS detector will be read out by approximately fifty thousand highspeed front-end optical links at an unprecedented data rate of up to 80 Tb/s, for an average expected total event size of approximately 8 − 10 MB. Following the present established design, the CMS trigger and data acquisition system will continue to feature two trigger levels, with only one synchronous hardware-based Level-1 Trigger (L1), consisting of custom electronic boards and operating on dedicated data streams, and a second level, the High Level Trigger (HLT), using software algorithms running asynchronously on standard processors and making use of the full detector data to select events for offline storage and analysis. The upgraded CMS data acquisition system will collect data fragments for Level-1 accepted events from the detector back-end modules at a rate up to 750 kHz, aggregate fragments corresponding to individual Level- 1 accepts into events, and distribute them to the HLT processors where they will be filtered further. Events accepted by the HLT will be stored permanently at a rate of up to 7.5 kHz. This paper describes the baseline design of the DAQ and HLT systems for the Phase-2 of CMS.

This paper outlines a software architecture where zero-copy operations are used comprehensively at every processing point from the Application layer to the Physical layer. The proposed architecture is being used during feasibility studies on advanced networking technologies for the CMS experiment at CERN. The design relies on a homogeneous peer-to-peer message passing system, which is built around memory pool caches allowing efficient and deterministic latency handling of messages of any size through the different software layers. In this scheme portable distributed applications can be programmed to process input to output operations by mere pointer arithmetic and DMA operations only. The approach combined with the open fabric protocol stack (OFED) allows one to attain near wire-speed message transfer at application level. The architecture supports full portability of user applications by encapsulating the protocol details and network into modular peer transport services whereas a transparent replacement of the underlying protocol facilitates deployment of several network technologies like Gigabit Ethernet, Myrinet, Infiniband, etc. Therefore, this solution provides a protocol-independent communication framework and prevents having to deal with potentially difficult couplings when the underlying communication infrastructure is changed. We demonstrate the feasibility of this approach by giving efficiency and performance measurements of the software in the context of the CMS distributed event building studies.

The data acquisition system for the CMS experiment at the Large Hadron Collider (LHC) will require a large and high performance event building network. Several switch technologies are currently being evaluated in order to compare different architectures for the event builder. One candidate is Myrinet. This paper describes the demonstrator which has been set up to study a small-scale (8/spl times/8) event builder based on a Myrinet switch. Measurements are presented on throughput, overhead and scaling for various traffic conditions. Results are shown on event building with a push architecture.

V. Brigljevic, G. Bruno, E. Cano, S. Cittolin, A. Csilling, D. Gigi, F. Glege, R. Gomez-Reino, M. Gulmini, J. Gutleber, C. Jacobs, M. Kozlovszky, H. Larsen, I. Magrans, F. Meijers, E. Meschi, S. Murray, A. Oh, L. Orsini, L. Pollet, A. Racz, D. Samyn, P. Scharff-Hansen, C. Schwick, P. Sphicas CERN, European Organization for Nuclear Research, Geneva, Switzerland Also at INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy Also at University of Athens, Greece L. Berti, G. Maron, G. Rorato, N. Toniolo, L. Zangrando INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy M. Bellato, S. Ventura INFN, Sezione di Padova, Padova, Italy S. Erhan University of California, Los Angeles, California, USA

Run control systems of modern high-energy particle physics experiments have requirements similar to those of today's Internet applications. The Compact Muon Solenoid (CMS) collaboration at CERN's Large Hadron Collider (LHC) therefore decided to build the run control system for its detector based on web technologies. The system is composed of Java Web Applications distributed over a set of Apache Tomcat servlet containers that connect to a database back-end. Users interact with the system through a web browser. The present paper reports on the successful scaling of the system from a small test setup to the production data acquisition system that comprises around 10.000 applications running on a cluster of about 1600 hosts. We report on operational aspects during the first phase of operation with colliding beams including performance, stability, integration with the CMS Detector Control System and tools to guide the operator.

The DAQ system of the CMS experiment at the LHC is upgraded during the accelerator shutdown in 2013/14. To reduce the interdependency of the DAQ system and the high-level trigger (HLT), we investigate the feasibility of using a file-system-based HLT. Events of ~1 MB size are built at the level-1 trigger rate of 100 kHz. The events are assembled by ~50 builder units (BUs). Each BU writes the raw events at ~2GB/s to a local file system shared with Q(10) filter-unit machines (FUs) running the HLT code. The FUs read the raw data from the file system, select Q(1%) of the events, and write the selected events together with monitoring meta-data back to a disk. This data is then aggregated over several steps and made available for offline reconstruction and online monitoring. We present the challenges, technical choices, and performance figures from the prototyping phase. In addition, the steps to the final system implementation will be discussed.

A flexible monitoring system has been designed for the CMS File-based Filter Farm making use of modern data mining and analytics components. All the metadata and monitoring information concerning data flow and execution of the HLT are generated locally in the form of small documents using the JSON encoding. These documents are indexed into a hierarchy of elasticsearch (es) clusters along with process and system log information. Elasticsearch is a search server based on Apache Lucene. It provides a distributed, multitenant-capable search and aggregation engine. Since es is schema-free, any new information can be added seamlessly and the unstructured information can be queried in non-predetermined ways. The leaf es clusters consist of the very same nodes that form the Filter Farm thus providing natural horizontal scaling. A separate central" es cluster is used to collect and index aggregated information. The fine-grained information, all the way to individual processes, remains available in the leaf clusters. The central es cluster provides quasi-real-time high-level monitoring information to any kind of client. Historical data can be retrieved to analyse past problems or correlate them with external information. We discuss the design and performance of this system in the context of the CMS DAQ commissioning for LHC Run 2.

The CMS data acquisition (DAQ) system relies on a purely software driven high level trigger (HLT) to reduce the full Level 1 accept rate of 100 kHz to approximately 100 Hz for archiving and later offline analysis. The HLT operates on the full information of events assembled by an event builder collecting detector data from the CMS front-end systems. The HLT software consists of a sequence of reconstruction and filtering modules executed on a farm of O(1000) CPUs built from commodity hardware. This paper presents the architecture of the CMS HLT, which integrates the CMS reconstruction framework in the online environment. The mechanisms to configure, control, and monitor the filter farm and the procedures to validate the filtering code within the DAQ environment are described.

The Compact Muon Solenoid (CMS) is a CERN multi-purpose experiment that exploits the physics of the Large Hadron Collider (LHC). The Detector Control System (DCS) is responsible for ensuring the safe, correct and efficient operation of the experiment, and has contributed to the recording of high quality physics data. The DCS is programmed to automatically react to the LHC operational mode. CMS sub-detectors' bias voltages are set depending on the machine mode and particle beam conditions. An operator provided with a small set of screens supervises the system status summarized from the approximately 6M monitored parameters. Using the experience of nearly two years of operation with beam the DCS automation software has been enhanced to increase the system efficiency by minimizing the time required by sub-detectors to prepare for physics data taking. From the infrastructure point of view the DCS will be subject to extensive modifications in 2012. The current rack mounted control PCs will be replaced by a redundant pair of DELL Blade systems. These blade servers are a high-density modular solution that incorporates servers and networking into a single chassis that provides shared power, cooling and management. This infrastructure modification associated with the migration to blade servers will challenge the DCS software and hardware factorization capabilities. The on-going studies for this migration together with the latest modifications are discussed in the paper.

The CMS experiment will be upgraded for operation at the HighLuminosity LHC to maintain and extend its physics performance under extreme pileup conditions. Upgrades will include an entirely new tracking system, supplemented by a track finder processor providing tracks at Level-1, as well as a high-granularity calorimeter in the endcap region. New front-end and back-end electronics will also provide the Level-1 trigger with high-resolution information from the barrel calorimeter and the muon systems. The upgraded Level-1 processors, based on powerful FPGAs, will be able to carry out sophisticated feature searches with resolutions often similar to the offline ones, while keeping pileup effects under control. In this paper, we discuss the feasibility of a system capturing Level-1 intermediate data at the beam-crossing rate of 40 MHz and carrying out online analyzes based on these limited-resolution data. This 40 MHz scouting system would provide fast and virtually unlimited statistics for detector diagnostics, alternative luminosity measurements and, in some cases, calibrations. It has the potential to enable the study of otherwise inaccessible signatures, either too common to fit in the Level-1 accept budget, or with requirements which are orthogonal to “mainstream” physics, such as long-lived particles. We discuss the requirements and possible architecture of a 40 MHz scouting system, as well as some of the physics potential, and results from a demonstrator operated at the end of Run-2 using the Global Muon Trigger data from CMS. Plans for further demonstrators envisaged for Run-3 are also discussed.

The data acquisition system (DAQ) of the CMS experiment at the CERN Large Hadron Collider (LHC) assembles events at a rate of 100 kHz, transporting event data at an aggregate throughput of more than 100GB/s to the Highlevel Trigger (HLT) farm. The HLT farm selects and classifies interesting events for storage and offline analysis at an output rate of around 1 kHz. The DAQ system has been redesigned during the accelerator shutdown in 2013-2014. The motivation for this upgrade was twofold. Firstly, the compute nodes, networking and storage infrastructure were reaching the end of their lifetimes. Secondly, in order to maintain physics performance with higher LHC luminosities and increasing event pileup, a number of sub-detectors are being upgraded, increasing the number of readout channels as well as the required throughput, and replacing the off-detector readout electronics with a MicroTCA-based DAQ interface. The new DAQ architecture takes advantage of the latest developments in the computing industry. For data concentration 10/40 Gbit/s Ethernet technologies are used, and a 56Gbit/s Infiniband FDR CLOS network (total throughput ≈ 4Tbit/s) has been chosen for the event builder. The upgraded DAQ - HLT interface is entirely file-based, essentially decoupling the DAQ and HLT systems. The fully-built events are transported to the HLT over 10/40 Gbit/s Ethernet via a network file system. The collection of events accepted by the HLT and the corresponding metadata are buffered on a global file system before being transferred off-site. The monitoring of the HLT farm and the data-taking performance is based on the Elasticsearch analytics tool. This paper presents the requirements, implementation, and performance of the system. Experience is reported on the first year of operation with LHC proton-proton runs as well as with the heavy ion lead-lead runs in 2015.

The data acquisition system for the CMS experiment at the Large Hadron Collider (LHC) will require a large and high performance event building network. Several switch technologies are currently being evaluated in order to compare different architectures for the event builder. One candidate is Myrinet. This paper describes the demonstrator which has been setup to study a small-scale (16×16) event builder based on PCs running Linux connected to Myrinet and Ethernet switches. A detailed study of the Myrinet switch performance has been performed for various traffic conditions, including the behaviour of composite switches. Results from event building studies are presented, including measurements on throughput, overhead and scaling. Traffic shaping techniques have been implemented and the effect on the event building performance has been investigated. The paper reports on performances and maximum event rate obtainable using custom software, not described, for the Myrinet control program and the low-level communication layer, implemented in a driver for Linux. A high performance sender is emulated by creating a dummy buffer that remains resident in the network interface and moving from the host only the first 64 bytes used by the event building protocol. An approximate scaling in N is presented assuming a balanced system where each source sends on average data to all destinations with the same rate.

The Run Control and Monitor System (RCMS) of the CMS experiment is the set of hardware and software components responsible for controlling and monitoring the experiment during data-taking. It provides users with a "virtual counting room", enabling them to operate the experiment and to monitor detector status and data quality from any point in the world. This paper describes the architecture of the RCMS with particular emphasis on its scalability through a distributed collection of nodes arranged in a tree-based hierarchy. The current implementation of the architecture in a prototype RCMS used in test beam setups, detector validations and DAQ demonstrators is documented. A discussion of the key technologies used, including Web Services, and the results of tests performed with a 128-node system are presented.

The CMS experiment at the CERN Large Hadron Collider is currently being commissioned and is scheduled to collect the first pp collision data in 2008. CMS features a two-level trigger system. The Level-1 trigger, based on custom hardware, is designed to reduce the collision rate of 40 MHz to approximately 100 kHz. Data for events accepted by the Level-1 trigger are read out and assembled by an Event Builder. The High Level Trigger (HLT) employs a set of sophisticated software algorithms, to analyze the complete event information, and further reduce the accepted event rate for permanent storage and analysis. This paper describes the design and implementation of the HLT Configuration Management system. First experiences with commissioning of the HLT system are also reported.

The Data Acquisition system of the Compact Muon Solenoid experiment at CERN assembles events at a rate of 100 kHz, transporting event data at an aggregate throughput of 100 GByte/s. We are presenting the design of the 2nd generation DAQ system, including studies of the event builder based on advanced networking technologies such as 10 and 40 Gbit/s Ethernet and 56 Gbit/s FDR Infiniband and exploitation of multicore CPU architectures. By the time the LHC restarts after the 2013/14 shutdown, the current compute nodes, networking, and storage infrastructure will have reached the end of their lifetime. In order to handle higher LHC luminosities and event pileup, a number of sub-detectors will be upgraded, increase the number of readout channels and replace the off-detector readout electronics with a μTCA implementation. The second generation DAQ system, foreseen for 2014, will need to accommodate the readout of both existing and new off-detector electronics and provide an increased throughput capacity. Advances in storage technology could make it feasible to write the output of the event builder to (RAM or SSD) disks and implement the HLT processing entirely file based.

The data-acquisition (DAQ) system of the CMS experiment at the LHC performs the read-out and assembly of events accepted by the first level hardware trigger. Assembled events are made available to the high-level trigger (HLT), which selects interesting events for offline storage and analysis. The system is designed to handle a maximum input rate of 100 kHz and an aggregated throughput of 100 GB/s originating from approximately 500 sources and 10^8 electronic channels. An overview of the architecture and design of the hardware and software of the DAQ system is given. We report on the performance and operational experience of the DAQ and its Run Control System in the first two years of collider runs of the LHC, both in proton-proton and Pb-Pb collisions. We present an analysis of the current performance, its limitations, and the most common failure modes and discuss the ongoing evolution of the HLT capability needed to match the luminosity ramp-up of the LHC.

We present the automation mechanisms that have been added to the Data Acquisition and Run Control systems of the Compact Muon Solenoid (CMS) experiment during Run 1 of the LHC, ranging from the automation of routine tasks to automatic error recovery and context-sensitive guidance to the operator. These mechanisms helped CMS to maintain a data taking efficiency above 90% and to even improve it to 95% towards the end of Run 1, despite an increase in the occurrence of single-event upsets in sub-detector electronics at high LHC luminosity.

The CMS online cluster consists of more than 2000 computers running about 10000 application instances. These applications implement the control of the experiment, the event building, the high level trigger, the online database and the control of the buffering and transferring of data to the Central Data Recording at CERN. In this paper the IT solutions employed to fulfil the requirements of such a large cluster are revised. Details are given on the chosen network structure, configuration management system, monitoring infrastructure and on the implementation of the high availability for the services and infrastructure.

The upgraded High Luminosity LHC, after the third Long Shutdown (LS3), will provide an instantaneous luminosity of 7.5 × 1034 cm−2s−1 (levelled), at the price of extreme pileup of up to 200 interactions per crossing. In LS3, the CMS Detector will also undergo a major upgrade to prepare for the phase-2 of the LHC physics program, starting around 2025. The upgraded detector will be read out at an unprecedented data rate of up to 50 Tb/s and an event rate of 750 kHz. Complete events will be analysed by software algorithms running on standard processing nodes, and selected events will be stored permanently at a rate of up to 10 kHz for offline processing and analysis.

TCP and the socket abstraction have barely changed over the last two decades, but at the network layer there has been a giant leap from a few megabits to 100 gigabits in bandwidth. At the same time, CPU architectures have evolved into the multi-core era and applications are expected to make full use of all available resources. Applications in the data acquisition domain based on the standard socket library running in a Non-Uniform Memory Access (NUMA) architecture are unable to reach full efficiency and scalability without the software being adequately aware about the IRQ (Interrupt Request), CPU and memory affinities. During the first long shutdown of LHC, the CMS DAQ system is going to be upgraded for operation from 2015 onwards and a new software component has been designed and developed in the CMS online framework for transferring data with sockets. This software attempts to wrap the low-level socket library to ease higher-level programming with an API based on an asynchronous event driven model similar to the DAT uDAPL API. It is an event-based application with NUMA optimizations, that allows for a high throughput of data across a large distributed system. This paper describes the architecture, the technologies involved and the performance measurements of the software in the context of the CMS distributed event building.

During the LHC Long Shutdown 1, the CMS Data Acquisition (DAQ) system underwent a partial redesign to replace obsolete network equipment, use more homogeneous switching technologies, and support new detector back-end electronics. The software and hardware infrastructure to provide input, execute the High Level Trigger (HLT) algorithms and deal with output data transport and storage has also been redesigned to be completely file- based. All the metadata needed for bookkeeping are stored in files as well, in the form of small documents using the JSON encoding. The Storage and Transfer System (STS) is responsible for aggregating these files produced by the HLT, storing them temporarily and transferring them to the T0 facility at CERN for subsequent offline processing. The STS merger service aggregates the output files from the HLT from ∼62 sources produced with an aggregate rate of ∼2GB/s. An estimated bandwidth of 7GB/s in concurrent read/write mode is needed. Furthermore, the STS has to be able to store several days of continuous running, so an estimated of 250TB of total usable disk space is required. In this article we present the various technological and implementation choices of the three components of the STS: the distributed file system, the merger service and the transfer system.

The CMS Data Acquisition System is designed to build and Alter events originating from 476 detector data sources at a maximum trigger rate of 100 KHz. Different architectures and switch technologies have been evaluated to accomplish this purpose. Events will be built in two stages: the first stage will be a set of event builders called FED Builders. These will be based on Myrinet technology and will pre-assemble groups of about 8 data sources. The second stage will be a set of event builders called Readout Builders. These will perform the building of full events. A single Readout Builder will build events from 72 sources of 16 KB fragments at a rate of 12.5 KHz. In this paper we present the design of a Readout Builder based on TCP/IP over Gigabit Ethernet and the optimization that was required to achieve the design throughput. This optimization includes architecture of the Readout Builder, the setup of TCP/IP, and hardware selection.

The Data Acquisition system of the Compact Muon Solenoid experiment at CERN assembles events at a rate of 100 kHz, transporting event data at an aggregate throughput of 100 GByte/s. We are presenting the design of the 2nd generation DAQ system, including studies of the event builder based on advanced networking technologies such as 10 and 40 Gbit/s Ethernet and 56 Gbit/s FDR Infiniband and exploitation of multicore CPU architectures. By the time the LHC restarts after the 2013/14 shutdown, the current compute nodes, networking, and storage infrastructure will have reached the end of their lifetime. In order to handle higher LHC luminosities and event pileup, a number of sub-detectors will be upgraded, increase the number of readout channels and replace the off-detector readout electronics with a μTCA implementation. The second generation DAQ system, foreseen for 2014, will need to accommodate the readout of both existing and new off-detector electronics and provide an increased throughput capacity. Advances in storage technology could make it feasible to write the output of the event builder to (RAM or SSD) disks and implement the HLT processing entirely file based.

The supervisory level of the Detector Control System (DCS) of the CMS experiment is implemented using Finite State Machines (FSM), which model the behaviours and control the operations of all the sub-detectors and support services. The FSM tree of the whole CMS experiment consists of more than 30.000 nodes. An analysis of a system of such size is a complex task but is a crucial step towards the improvement of the overall performance of the FSM system. This paper presents the analysis of the CMS FSM system using the micro Common Representation Language 2 (mcrl2) methodology. Individual mCRL2 models are obtained for the FSM systems of the CMS sub-detectors using the ASF+SDF automated translation tool. Different mCRL2 operations are applied to the mCRL2 models. A mCRL2 simulation tool is used to closer examine the system. Visualization of a system based on the exploration of its state space is enabled with a mCRL2 tool. Requirements such as command and state propagation are expressed using modal mu-calculus and checked using a model checking algorithm. For checking local requirements such as endless loop freedom, the Bounded Model Checking technique is applied. This paper discusses these analysis techniques and presents the results of their application on the CMS FSM system.

The CMS detector control system (DCS) is responsible for controlling and monitoring the detector status and for the operation of all CMS sub detectors and infrastructure. This is required to ensure safe and efficient data taking so that high quality physics data can be recorded. The current system architecture is composed of more than 100 servers in order to provide the required processing resources. An optimization of the system software and hardware architecture is under development to ensure redundancy of all the controlled subsystems and to reduce any downtime due to hardware or software failures. The new optimized structure is based mainly on powerful and highly reliable blade servers and makes use of a fully redundant approach, guaranteeing high availability and reliability. The analysis of the requirements, the challenges, the improvements and the optimized system architecture as well as its specific hardware and software solutions are presented.

Summary form only given. The data acquisition system (DAQ) of the CMS experiment at the CERN Large Hadron Collider assembles events at a rate of 100 kHz, transporting event data at an aggregate throughput of 100 GB/s to the high level trigger (HLT) farm. The HLT farm selects interesting events for storage and offline analysis at a rate of around 1 kHz. The DAQ system has been redesigned during the accelerator shutdown in 2013/14. The motivation is twofold: Firstly, the current compute nodes, networking, and storage infrastructure will have reached the end of their lifetime by the time the LHC restarts. Secondly, in order to handle higher LHC luminosities and event pileup, a number of sub-detectors will be upgraded, increasing the number of readout channels and replacing the off-detector readout electronics with a μTCA implementation. The new DAQ architecture will take advantage of the latest developments in the computing industry. For data concentration, 10/40 Gb/s Ethernet technologies will be used, as well as an implementation of a reduced TCP/IP in FPGA for a reliable transport between custom electronics and commercial computing hardware. A 56 Gb/s Infiniband FDR Clos network has been chosen for the event builder with a throughput of ~4 Tb/s. The HLT processing is entirely file based. This allows the DAQ and HLT systems to be independent, and to use the HLT software in the same way as for the offline processing. The fully built events are sent to the HLT with 1/10/40 Gb/s Ethernet via network file systems. Hierarchical collection of HLT accepted events and monitoring meta-data are stored into a global file system. This paper presents the requirements, technical choices, and performance of the new system.

The CMS detector will undergo a major upgrade for the Phase-2 of theLHC program the High-Luminosity LHC.The upgraded CMS detector willbe read out at an unprecedented data rate exceed-ing50 Tb/s, with a Level-1 trigger selecting eventsat a rate of 750 kHz, and an average event size reaching8.5MB.The Phase-2 CMS back-end electronics will bebased on the ATCA standard, with node boards receiving the detectordata from the front-ends via custom, radiation-tolerant, opticallinks.The CMS Phase-2 data acquisition (DAQ) design tightens the integrationbetween trigger control and data flow, extending the synchronousregime of the DAQ system.At the core of the design is the DAQ andTiming Hub, a custom ATCA hub card forming the bridge between thedifferent, detectorspecific, control and readout electronics and thecommon timing, trigger, and control systems.The overall synchronisation and data flow of the experiment is handledby the Trigger and Timing Control and Distribution System (TCDS).Forincreased flexibility during commissioning and calibration runs, thePhase-2 architecture breaks with the traditional distribution tree, infavour of a configurable network connecting multiple independentcontrol units to all off-detector endpoints.This paper describes the overall Phase-2 TCDS architecture, andbriefly compares it to previous CMS implementations.It then discussesthe design and prototyping experience of the DTH, and concludes withthe convergence of this prototyping process into the (pre)productionphase, starting in early 2023.

A comprehensive model based on XML technologies to interface data acquisition hardware devices for configuration and control purposes is presented. The model builds upon the use of a unified syntax for describing hardware devices, configuration data, test results and control sequences. An implementation and an evaluation together with an application scenario are presented.

The Trigger Throttling System (TTS) adapts the trigger frequency to the DAQ readout capacity in order to avoid buffer overflows and data corruption. The states of all ~640 readout units in the CMS DAQ are read out and merged by hardware modules (FMMs) to obtain the status of each detector partition. The functionality and the design of the second and final prototype of the FMM are presented in this paper.

The CMS experiment will collect data from the proton-proton collisions delivered by the Large Hadron Collider (LHC) at a centre-of-mass energy up to 14 TeV. The CMS trigger system is designed to cope with unprecedented luminosities and LHC bunch-crossing rates up to 40 MHz. The unique CMS trigger architecture only employs two trigger levels. The Level-1 trigger is implemented using custom electronics, while the High Level Trigger (HLT) is based on software algorithms running on a large cluster of commercial processors, the Event Filter Farm. We present the major functionalities of the CMS High Level Trigger system as of the starting of LHC beams operations in September 2008. The validation of the HLT system in the online environment with Monte Carlo simulated data and its commissioning during cosmic rays data taking campaigns are discussed in detail. We conclude with the description of the HLT operations with the first circulating LHC beams before the incident occurred the 19th September 2008.

The primary goal of the online cluster of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) is to build event data from the detector and to select interesting collisions in the High Level Trigger (HLT) farm for offline storage. With more than 1500 nodes and a capacity of about 850 kHEPSpecInt06, the HLT machines represent similar computing capacity of all the CMS Tier1 Grid sites together. Moreover, it is currently connected to the CERN IT datacenter via a dedicated 160 Gbps network connection and hence can access the remote EOS based storage with a high bandwidth. In the last few years, a cloud overlay based on OpenStack has been commissioned to use these resources for the WLCG when they are not needed for data taking. This online cloud facility was designed for parasitic use of the HLT, which must never interfere with its primary function as part of the DAQ system. It also allows to abstract from the different types of machines and their underlying segmented networks. During the LHC technical stop periods, the HLT cloud is set to its static mode of operation where it acts like other grid facilities. The online cloud was also extended to make dynamic use of resources during periods between LHC fills. These periods are a-priori unscheduled and of undetermined length, typically of several hours, once or more a day. For that, it dynamically follows LHC beam states and hibernates Virtual Machines (VM) accordingly. Finally, this work presents the design and implementation of a mechanism to dynamically ramp up VMs when the DAQ load on the HLT reduces towards the end of the fill.

Mainstream computing equipment and the advent of affordable multi-Gigabit communication technology permit us to address grand-challenge data acquisition and processing problems with clusters of inexpensive computers. Such networks typically incorporate heterogeneous equipment, real-time partitions and even custom devices. Vital overall system requirements are high efficiency and flexibility. In preceding projects we experienced the difficulties to cover both requirements at once. Intelligent I/O (I/sub 2/O) is an industry specification that defines a uniform messaging format and execution environment for hardwareand operating system independent device drivers in computing systems with processor based communication equipment. Mapping this concept to a distributed computing environment and encapsulating the details of the specification into an application-programming framework allow us to provide architectural support for (i) efficient and (ii) extensible cluster operation. This paper portrays our view of applying I/sub 2/O to high-performance clusters. We demonstrate the feasibility of this approach by giving efficiency measurements of our XDAQ software framework for distributed data acquisition systems.

The data acquisition system of the CMS experiment at the Large Hadron Collider will employ an event builder which will combine data from about 500 data sources into full events at an aggregate throughput of 100 GByte/s. Several architectures and switch technologies have been evaluated for the DAQ Technical Design Report by measurements with test benches and by simulation. This paper describes studies of an EVB test-bench based on 64 PCs acting as data sources and data consumers and employing both Gigabit Ethernet and Myrinet technologies as the interconnect. In the case of Ethernet, protocols based on Layer-2 frames and on TCP/IP are evaluated. Results from ongoing studies, including measurements on throughput and scaling are presented. The architecture of the baseline CMS event builder will be outlined. The event builder is organised into two stages with intelligent buffers in between. The first stage contains 64 switches performing a first level of data concentration by building super-fragments from fragments of 8 data sources. The second stage combines the 64 super-fragments into full events. This architecture allows installation of the second stage of the event builder in steps, with the overall throughput scaling linearly with the number of switches in the second stage. Possible implementations of the components of the event builder are discussed and the expected performance of the full event builder is outlined.

CMS has adopted S-LINK64 [1] as the standard interface between the detector front end readout and the central Data Acquisition (DAQ) system. The S-LINK64 is a specification of a FIFO-like interface. This includes mechanical descriptions of connector and daughter board format and electrical signal definition. The hardware/software package described in this paper (FEDkit) emulates the central DAQ side of this interface at the data rate required by the final DAQ system. The performance, integration with the CMS DAQ software framework, and plans for future developments for the DAQ input interface are also presented.

The CMS central DAQ system is built using commercial hardware (PCs and networking equipment), except for two components: the Front-end Readout Link (FRL) and the Fast Merger Module (FMM). The FRL interfaces the sub-detector specific front-end electronics to the central DAQ system in a uniform way. The FRL is a compact-PCI module with an additional PCI 64bit connector to host a Network Interface Card (NIC). On the sub-detector side, the data are written to the link using a FIFO-like protocol (SLINK64). The link uses the Low Voltage Differential Signal (LVDS) technology to transfer data with a throughput of up to 400 MBytes/s. The FMM modules collect status signals from the front-end electronics of the sub-detectors, merge and monitor them and provide the resulting signals with low latency to the first level trigger electronics. In particular, the throttling signals allow the trigger to avoid buffer overflows and data corruption in the front-end electronics when the data produced in the front-end exceeds the capacity of the DAQ system. Both cards are compact-PCI cards with a 6U form factor. They are implemented with FPGAs. The main FPGA implements the processing logic of the card and the interfaces to the variety of busses on the card. Another FPGA contains a custom compact-PCI interface for configuration, control and monitoring. The chosen technology provides flexibility to implement new features if required.

The Compact Muon Solenoid (CMS) experiment has developed an electrical implementation of the S-LINK64 extension (Simple Link Interface 64 bit) operating at 400 MB/s in order to read out the detector. This paper studies a possible replacement of the existing S-LINK64 implementation by an optical link, based on 10 Gigabit Ethernet in order to fulfil larger throughput, replace aging hardware and simplify an architecture. A prototype transmitter unit has been developed based on the FPGA Altera PCI Express Development Kit with a custom firmware. A standard PC has been acted as receiving unit. The data transfer has been implemented on a stack of protocols: RDP over IP over Ethernet. This allows receiving the data by standard hardware components like PCs or network switches and NICs. The first test proved that basic exchange of the packets between transmitter and receiving unit works. The paper summarizes the status of these studies.

The data acquisition system (DAQ) of the CMS experiment at the CERN Large Hadron Collider (LHC) assembles events at a rate of 100 kHz, transporting event data at an aggregate throughput of 100GB/s to the high-level trigger (HLT) farm. The DAQ system has been redesigned during the LHC shutdown in 2013/14. The new DAQ architecture is based on state-of-the-art network technologies for the event building. For the data concentration, 10/40 Gbps Ethernet technologies are used together with a reduced TCP/IP protocol implemented in FPGA for a reliable transport between custom electronics and commercial computing hardware. A 56 Gbps Infiniband FDR CLOS network has been chosen for the event builder. This paper discusses the software design, protocols, and optimizations for exploiting the hardware capabilities. We present performance measurements from small-scale prototypes and from the full-scale production system.

During the LHC Long Shutdown 1, the CMS Data Acquisition system underwent a partial redesign to replace obsolete network equipment, use more homogeneous switching technologies, and prepare the ground for future upgrades of the detector front-ends. The software and hardware infrastructure to provide input, execute the High Level Trigger (HLT) algorithms and deal with output data transport and storage has also been redesigned to be completely file- based. This approach provides additional decoupling between the HLT algorithms and the input and output data flow. All the metadata needed for bookkeeping of the data flow and the HLT process lifetimes are also generated in the form of small "documents" using the JSON encoding, by either services in the flow of the HLT execution (for rates etc.) or watchdog processes. These "files" can remain memory-resident or be written to disk if they are to be used in another part of the system (e.g. for aggregation of output data). We discuss how this redesign improves the robustness and flexibility of the CMS DAQ and the performance of the system currently being commissioned for the LHC Run 2.

A Software environment to describe configuration, control and test systems for data acquisition hardware devices is presented. The design follows a model that enforces a comprehensive use of an extensible markup language (XML) syntax to describe both the code and associated data. A feasibility study of this software, carried out for the CMS experiment at CERN, is also presented. This is based on a number of standalone applications for different hardware modules, and the design of a hardware management system to remotely access to these heterogeneous subsystems through a uniform web service interface.

The error and alarm system for the data acquisition of the Compact Muon Solenoid (CMS) at CERN was successfully used for the physics runs at Large Hadron Collider (LHC) during first three years of activities. Error and alarm processing entails the notification, collection, storing and visualization of all exceptional conditions occurring in the highly distributed CMS online system using a uniform scheme. Alerts and reports are shown on-line by web application facilities that map them to graphical models of the system as defined by the user. A persistency service keeps a history of all exceptions occurred, allowing subsequent retrieval of user defined time windows of events for later playback or analysis. This paper describes the architecture and the technologies used and deals with operational aspects during the first years of LHC operation. In particular we focus on performance, stability, and integration with the CMS sub-detectors.

The CMS experiment at the LHC uses a two-stage trigger system, with events flowing from the first level trigger at a rate of 100 kHz. These events are read out by the Data Acquisition system (DAQ), assembled in memory in a farm of computers, and finally fed into the high-level trigger (HLT) software running on the farm. The HLT software selects interesting events for offline storage and analysis at a rate of a few hundred Hz. The HLT algorithms consist of sequences of offline-style reconstruction and filtering modules, executed on a farm of 0(10000) CPU cores built from commodity hardware. Experience from the 2010–2011 collider run is detailed, as well as the current architecture of the CMS HLT, and its integration with the CMS reconstruction framework and CMS DAQ. The short- and medium-term evolution of the HLT software infrastructure is discussed, with future improvements aimed at supporting extensions of the HLT computing power, and addressing remaining performance and maintenance issues.

The Data Acquisition system of the Compact Muon Solenoid experiment at CERN assembles events at a rate of 100 kHz, transporting event data at an aggregate throughput of 100 GB/s. By the time the LHC restarts after the 2013/14 shut-down, the current computing and networking infrastructure will have reached the end of their lifetime. This paper presents design studies for an upgrade of the CMS event builder based on advanced networking technologies such as 10/40 Gb/s Ethernet and Infiniband. The results of performance measurements with small-scale test setups are shown.

The Run Control System of the Compact Muon Solenoid (CMS) experiment at CERN's new Large Hadron Collider (LHC) controls the sub-detector and central data acquisition systems and the high-level trigger farm of the experiment. It manages around 10,000 applications that control custom hardware or handle the event building and the high-level trigger processing. The CMS Run Control System is a distributed Java system running on a set of Apache Tomcat servlet containers. Users interact with the system through a web browser. The paper presents the architecture of the CMS Run Control System and deals with operational aspects during the first phase of operation with colliding beams. In particular it focuses on performance, stability, integration with the CMS Detector Control System, integration with LHC status information and tools to guide the shifter.

After two years of maintenance and upgrade, the Large Hadron Collider (LHC), the largest and most powerful particle accelerator in the world, has started its second three year run. Around 1500 computers make up the CMS (Compact Muon Solenoid) Online cluster. This cluster is used for Data Acquisition of the CMS experiment at CERN, selecting and sending to storage around 20 TBytes of data per day that are then analysed by the Worldwide LHC Computing Grid (WLCG) infrastructure that links hundreds of data centres worldwide. 3000 CMS physicists can access and process data, and are always seeking more computing power and data. The backbone of the CMS Online cluster is composed of 16000 cores which provide as much computing power as all CMS WLCG Tier1 sites (352K HEP-SPEC-06 score in the CMS cluster versus 300K across CMS Tier1 sites). The computing power available in the CMS cluster can significantly speed up the processing of data, so an effort has been made to allocate the resources of the CMS Online cluster to the grid when it isn’t used to its full capacity for data acquisition. This occurs during the maintenance periods when the LHC is non-operational, which corresponded to 117 days in 2015. During 2016, the aim is to increase the availability of the CMS Online cluster for data processing by making the cluster accessible during the time between two physics collisions while the LHC and beams are being prepared. This is usually the case for a few hours every day, which would vastly increase the computing power available for data processing. Work has already been undertaken to provide this functionality, as an OpenStack cloud layer has been deployed as a minimal overlay that leaves the primary role of the cluster untouched. This overlay also abstracts the different hardware and networks that the cluster is composed of. The operation of the cloud (starting and stopping the virtual machines) is another challenge that has been overcome as the cluster has only a few hours spare during the aforementioned beam preparation. By improving the virtual image deployment and integrating the OpenStack services with the core services of the Data Acquisition on the CMS Online cluster it is now possible to start a thousand virtual machines within 10 minutes and to turn them off within seconds. This document will explain the architectural choices that were made to reach a fully redundant and scalable cloud, with a minimal impact on the running cluster configuration while giving a maximal segregation between the services. It will also present how to cold start 1000 virtual machines 25 times faster, using tools commonly utilised in all data centres.

The front-end electronics of the CMS experiment will be read out in parallel into approximately 650 modules which will be located in the underground counting room. The data read out will then be transported over a distance of ~200 m to the surface counting room where they will be received into deep buffers, the Readout Units. The latter also provide the first step in the CMS event building process, by combining the data from multiple detector data sources into larger-size (~16 kB) data fragments. The second and final event-building step merges 64 such super-fragments into a full event. The first stage of the Event Builder, referred to as the Data to Surface (D2S) system is structured in a way to allow for a modular and scalable DAQ system whose performance can grow with the increasing luminosity of the LHC

Traditional systems dominated by performance constraints tend to neglect other qualities such as maintainability and configurability. Object-Orientation allows one to encapsulate the technology differences in communication sub-systems and to provide a uniform view of data transport layer to the systems engineer. We applied this paradigm to the design and implementation of intelligent data servers in the Compact Muon Solenoid (CMS) data acquisition system at CERN to easily exploiting the physical communication resources of the available equipment. CMS is a high-energy physics experiment under study that incorporates a highly distributed data acquisition system. This paper outlines the architecture of one part, the so called Readout Unit, and shows how we can exploit the object advantage for systems with specific data rate requirements. A C++ streams communication layer with zero copying functionality has been established for UDP, TCP, DLPI and specific Myrinet and VME bus communication on the VxWorks real-time operating system. This software provides performance close to the hardware channel and hides communication details from the application programmers.

The data acquisition system of the CMS experiment at the Large Hadron Collider features a two-stage event builder, which combines data from about 500 sources into full events at an aggregate throughput of 100 GB/s. To meet the requirements, several architectures and interconnect technologies have been quantitatively evaluated. Myrinet will be used for the communication from the underground frontend devices to the surface event building system. Gigabit Ethernet is deployed in the surface event building system. Nearly full bi-section throughput can be obtained using a custom software driver for Myrinet based on barrel shifter traffic shaping. This paper discusses the use of Myrinet dual-port network interface cards supporting channel bonding to achieve virtual 5 GBit/s links with adaptive routing to alleviate the throughput limitations associated with wormhole routing. Adaptive routing is not expected to be suitable for high-throughput event builder applications in high-energy physics. To corroborate this claim, results from the CMS event builder preseries installation at CERN are presented and the problems of wormhole routing networks are discussed.

In order to accommodate new back-end electronics of upgraded CMS sub-detectors, a new FEROL40 card in the microTCA standard has been developed. The main function of the FEROL40 is to acquire event data over multiple point-to-point serial optical links, provide buffering, perform protocol conversion, and transmit multiple TCP/IP streams (4x10Gbps) to the Ethernet network of the aggregation layer of the CMS DAQ (data acquisition) event builder. This contribution discusses the design of the FEROL40 and experience from operation

The data acquisition system of the Compact Muon Solenoid experiment at the large hadron collider reads out event fragments of an average size of 2 kilobytes from around 650 detector front-ends at a rate of up to 100 kHz. The first stage of event-building is performed by the Super-Fragment Builder employing custom-built electronics and a Myrinet optical network. It reduces the number of fragments by one order of magnitude, thereby greatly decreasing the requirements for the subsequent event-assembly stage. By providing fast feedback from any of the front-ends to the trigger, the trigger throttling system prevents buffer overflows in the front-end electronics due to variations in the size and rate of events or due to backpressure from the down-stream event-building and processing. This paper reports on the recent successful integration of a scaled-down setup of the described system with the trigger and with front-ends of all major sub-detectors and discusses the ongoing commissioning of the full-scale system.

The CMS Data Acquisition (DAQ) System relies on a purely software driven High Level Trigger (HLT) to reduce the full Level-1 accept rate of 100 kHz to approximately 100 Hz for archiving and later offline analysis. The HLT operates on the full information of events assembled by an event builder collecting detector data from the CMS front-end systems. The HLT software consists of a sequence of reconstruction and filtering modules executed on a farm of 0(1000) CPUs built from commodity hardware. This paper presents the architecture of the CMS HLT, which integrates the CMS reconstruction framework in the online environment. The mechanisms to configure, control, and monitor the Filter Farm and the procedures to validate the filtering code within the DAQ environment are described.

The CMS detector will undergo a major upgrade for Phase-2 of the LHC program, starting around 2026.The upgraded Level-1 hardware trigger will select events at a rate of 750 kHz.At an expected event size of 7.4 MB this corresponds to a data rate of up to 50 Tbit/s.Optical links will carry the signals from on-detector front-end electronics to back-end electronics in ATCA crates in the service cavern.A DAQ and Timing Hub board aggregates data streams from back-end boards over point-to-point links, provides buffering and transmits the data to the commercial data-to-surface network for processing and storage.This hub board is also responsible for the distribution of timing, control and trigger signals to the back-ends.This paper presents the current development towards the DAQ and Timing Hub and the design of the first prototype, to be used as for validation and integration with the first back-end prototypes in 2019-2020.

The data acquisition (DAQ) system of the Compact Muon Solenoid (CMS) at CERN reads out the detector at the level-1 trigger accept rate of 100 kHz, assembles events with a bandwidth of 200 GB/s, provides these events to the high level-trigger running on a farm of about 30k cores and records the accepted events. Comprising custom-built and cutting edge commercial hardware and several 1000 instances of software applications, the DAQ system is complex in itself and failures cannot be completely excluded. Moreover, problems in the readout of the detectors,in the first level trigger system or in the high level trigger may provoke anomalous behaviour of the DAQ systemwhich sometimes cannot easily be differentiated from a problem in the DAQ system itself. In order to achieve high data taking efficiency with operators from the entire collaboration and without relying too heavily on the on-call experts, an expert system, the DAQ-Expert, has been developed that can pinpoint the source of most failures and give advice to the shift crew on how to recover in the quickest way. The DAQ-Expert constantly analyzes monitoring data from the DAQ system and the high level trigger by making use of logic modules written in Java that encapsulate the expert knowledge about potential operational problems. The results of the reasoning are presented to the operator in a web-based dashboard, may trigger sound alerts in the control room and are archived for post-mortem analysis - presented in a web-based timeline browser. We present the design of the DAQ-Expert and report on the operational experience since 2017, when it was first put into production.

The part of the CMS Data Acquisition (DAQ) system responsible for data readout and event building is a complex network of interdependent distributed applications. To ensure successful data taking, these programs have to be constantly monitored in order to facilitate the timeliness of necessary corrections in case of any deviation from specified behaviour. A large number of diverse monitoring data samples are periodically collected from multiple sources across the network. Monitoring data are kept in memory for online operations and optionally stored on disk for post-mortem analysis. We present a generic, reusable solution based on an open source NoSQL database, Elasticsearch, which is fully compatible and non-intrusive with respect to the existing system. The motivation is to benefit from an offthe-shelf software to facilitate the development, maintenance and support efforts. Elasticsearch provides failover and data redundancy capabilities as well as a programming language independent JSON-over-HTTP interface. The possibility of horizontal scaling matches the requirements of a DAQ monitoring system. The data load from all sources is balanced by redistribution over an Elasticsearch cluster that can be hosted on a computer cloud. In order to achieve the necessary robustness and to validate the scalability of the approach the above monitoring solution currently runs in parallel with an existing in-house developed DAQ monitoring system.

The Data Acquisition (DAQ) system of the Compact Muon Solenoid (CMS) experiment at the LHC is a complex system responsible for the data readout, event building and recording of accepted events. Its proper functioning plays a critical role in the data-taking efficiency of the CMS experiment. In order to ensure high availability and recover promptly in the event of hardware or software failure of the subsystems, an expert system, the DAQ Expert, has been developed. It aims at improving the data taking efficiency, reducing the human error in the operations and minimising the on-call expert demand. Introduced in the beginning of 2017, it assists the shift crew and the system experts in recovering from operational faults, streamlining the post mortem analysis and, at the end of Run 2, triggering fully automatic recovery without human intervention. DAQ Expert analyses the real-time monitoring data originating from the DAQ components and the high-level trigger updated every few seconds. It pinpoints data flow problems, and recovers them automatically or after given operator approval. We analyse the CMS downtime in the 2018 run focusing on what was improved with the introduction of automated recovery; present challenges and design of encoding the expert knowledge into automated recovery jobs. Furthermore, we demonstrate the web-based, ReactJS interfaces that ensure an effective cooperation between the human operators in the control room and the automated recovery system. We report on the operational experience with automated recovery.

The data acquisition system of the CMS experiment, at the CERN LHC collider, is designed to build 1 MB events at a sustained rate of 100 kHz and to provide sufficient computing power to filter the events by a factor of 1000. The data to surface (D2S) system is the first layer of the data acquisition interfacing the underground subdetector readout electronics to the surface event builder. It collects the 100 GB/s input data from a large number of front-end cards (650), implements a first stage event building by combining multiple sources into larger-size data fragments, and transports them to the surface for the full event building. The data to surface system can operate at the maximum rate of 2 Tbps. This paper describes the layout, reconfigurability and production validation of the D2S system which is to be installed by December 2005

HyperDAQ was conceived to give users access to distributed data acquisition systems easily. To achieve that, we marry two well-established technologies: the World Wide Web and Peer-to-Peer systems. An embedded HTTP protocol engine turns an executable program into a browsable Web application that can reflect its internal data structures using a data serialization package. While the Web is based on static hyperlinks to destinations known at the time of page creation, HyperDAQ creates links to data content providers dynamically. Peer-to-Peer technology enables adaptive navigation from one application to another depending on the lifetime of application modules. Traditionally, distributed systems give the user a single point of access. We take a radically different approach. Every node may become an access point from which the whole system can be explored.

The High Level Trigger (HLT) system of the CMS experiment will consist of a series of reconstruction and selection algorithms designed to reduce the Level-1 trigger accept rate of 100 kHz to 100 Hz forwarded to permanent storage. The HLT operates on events assembled by an event builder collecting detector data from the CMS front-end system at full granularity and resolution. The HLT algorithms will run on a farm of commodity PCs, the filter farm, with a total expected computational power of 10/sup 6/ SpecInt95. The farm software, responsible for collecting, analyzing, and storing event data, consists of components from the data acquisition and the offline reconstruction domains, extended with the necessary glue components and implementation of interfaces between them. The farm is operated and monitored by the DAQ control system and must provide near-real-time feedback on the performance of the detector and the physics quality of data. In this paper, the architecture of the HLT farm is described, and the design of various software components reviewed. The status of software development is presented, with a focus on the integration issues. The physics and CPU performance of current reconstruction and selection algorithm prototypes is summarized in relation with projected parameters of the farm and taking into account the requirements of the CMS physics program. Results from a prototype test stand and plans for the deployment of the final system are finally discussed.

A comprehensive model based on XML technologies to interface data acquisition hardware devices for configuration and control purposes is presented. The model builds upon the use of a unified syntax for describing hardware devices, configuration data, test results as well as control sequences. The integration of the model with the online software framework of the CMS experiment is under evaluation.

The Fast Merging Module (FMM) is part of the Trigger Throttling System (TTS). The TTS adapts the trigger frequency to the DAQ capacity in order to avoid congestions and overflows. The states of all data sources (~640 in the case of CMS) are read out and merged by the FMM to obtain the status of each detector partition. The functionality and the design of the FMM are presented in this paper.

The DAQ system of the CMS experiment at CERN collects data from more than 600 custom detector Front-End Drivers (FEDs). During 2013 and 2014 the CMS DAQ system will undergo a major upgrade to address the obsolescence of current hardware and the requirements posed by the upgrade of the LHC accelerator and various detector components. For a loss-less data collection from the FEDs a new FPGA based card implementing the TCP/IP protocol suite over 10Gbps Ethernet has been developed. To limit the TCP hardware implementation complexity the DAQ group developed a simplified and unidirectional but RFC 793 compliant version of the TCP protocol. This allows to use a PC with the standard Linux TCP/IP stack as a receiver. We present the challenges and protocol modifications made to TCP in order to simplify its FPGA implementation. We also describe the interaction between the simplified TCP and Linux TCP/IP stack including the performance measurements.

A flexible monitoring system has been designed for the CMS File-based Filter Farm making use of modern data mining and analytics components. All the metadata and monitoring information concerning data flow and execution of the HLT are generated locally in the form of small documents using the JSON encoding. These documents are indexed into a hierarchy of elasticsearch (es) clusters along with process and system log information. Elasticsearch is a search server based on Apache Lucene. It provides a distributed, multitenant-capable search and aggregation engine. Since es is schema-free, any new information can be added seamlessly and the unstructured information can be queried in non-predetermined ways. The leaf es clusters consist of the very same nodes that form the Filter Farm thus providing natural horizontal scaling. A separate central” es cluster is used to collect and index aggregated information. The fine-grained information, all the way to individual processes, remains available in the leaf clusters. The central es cluster provides quasi-real-time high-level monitoring information to any kind of client. Historical data can be retrieved to analyse past problems or correlate them with external information. We discuss the design and performance of this system in the context of the CMS DAQ commissioningmore » for LHC Run 2.« less

TCP and the socket abstraction have barely changed over the last two decades, but at the network layer there has been a giant leap from a few megabits to 100 gigabits in bandwidth. At the same time, CPU architectures have evolved into the multicore era and applications are expected to make full use of all available resources. Applications in the data acquisition domain based on the standard socket library running in a Non-Uniform Memory Access (NUMA) architecture are unable to reach full efficiency and scalability without the software being adequately aware about the IRQ (Interrupt Request), CPU and memory affinities. During the first long shutdown of LHC, the CMS DAQ system is going to be upgraded for operation from 2015 onwards and a new software component has been designed and developed in the CMS online framework for transferring data with sockets. This software attempts to wrap the low-level socket library to ease higher-level programming with an API based on an asynchronous event driven model similar to the DAT uDAPL API. It is an event-based application with NUMA optimizations, that allows for a high throughput of data across a large distributed system. This paper describes the architecture, the technologies involved and the performance measurements of the software in the context of the CMS distributed event building.

The CMS experiment at the LHC features over 2'500 devices that need constant monitoring in order to ensure proper data taking. The monitoring solution has been migrated from Nagios to Icinga, with several useful plugins. The motivations behind the migration and the selection of the plugins are discussed.

Scalable, distributed reactive systems require a scalable control infrastructure. Being able to model such an infrastructure is a prerequisite for putting it into place. In current systems, finite state machine based approaches are prevailing. They are, however, limited by their nature and hamper further improvements. Extensions like state charts have emerged to alleviate those shortcomings. Despite all this work, the proposed improvements do not live up to the requirements of continuously operating distributed systems. Therefore we look for alternatives that break with the underlying state-based model. Workflow systems recently became mature enough to be considered for use cases going beyond small-scale business applications. The concept on which they build is promising to scale to large systems. This paper compares various modeling technologies using the real-world scenario of distributed data acquisition systems as we find them in currently operating high-energy physics installations at the Large Hadron Collider at CERN. The outcome of our qualitative evaluation will show that current finite state machine compared to workflow based approaches have a bigger gap between specification and executed processes. Consequently workflow based approaches are better suited for the use case at hand and require less custom software extensions to reduce the remaining gap.