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Title: The new CMS DAQ system for run-2 of the LHC

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 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 Clos network based on 56 Gb/s FDR Infiniband has been chosen for the event builder with a throughput of ~ 4more » 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. As a result, this paper presents the requirements, technical choices, and performance of the new system.« less
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  1. European Organization for Nuclear Research (CERN), Geneva (Switzerland)
  2. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
  3. Univ. of California San Diego, La Jolla, CA (United States)
  4. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  5. Univ. of California, Los Angeles, CA (United States)
  6. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0018-9499; 1416731
Grant/Contract Number:
Accepted Manuscript
Journal Name:
IEEE Transactions on Nuclear Science
Additional Journal Information:
Journal Volume: 62; Journal Issue: 3; Journal ID: ISSN 0018-9499
Institute of Electrical and Electronics Engineers (IEEE)
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; data acquisition; high energy physics; Large Hadron Collider; throughput; file systems; aggregates; readout electronics computer architecture
OSTI Identifier: