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The CMS Event Builder Demonstrators based on Giga Ethernet switched Network

Marco Bellato1, Luciano Berti2, Michele Gulmini2, Gaetano Maron2, Nicola Toniolo2, Gabriele Vedovato2, Sandro Ventura3, XiaoQinq Yang2
  1. INFN - Sez Padova
  2. INFN - Lab. Naz. di Legnaro
  3. INFN - Sez. Padova

Speaker: Luciano Berti

  The LHC 40 MHz collision rate will produce in the CMS (Compact Muon Solenoid - one of the four LHC experiments) detector 10**9 interaction per second (100 Tbyte/s) . This input rate will be reduced (by the level 1 trigger subsystem) to 100 KHz and 100 Gbyte/s before being handled by the data acquisition system (Daq). Based on a high performance switched network, with the functions of event builder, connecting about 500 sub-detector readout units (RU) to about 500 builder units (BU) (each of which implemented by a computer farm), the CMS Daq system must provide the necessary bandwidth to assemble event fragments from many front-end buffers to a single location, and insure the sufficient computing power to lower down the final accepted event rate to about 100 Hz. The whole event data flow will be supervised by an event manager system (EVM). The event builder switched network is thus one of the more challenging point of the CMS daq and required the set up of reduced scale event builder demonstrators to evaluate both the more adequate switching technology and the more efficient protocol to be used in the final system. This contribution will focus mainly on small scale event builder demonstrators (currently up to 8x8) which have been set up to study the giga ethernet technology. Aggregate throughput both in terms of bandwidth and event builder rate under realistic conditions are presented using as RUs and BUs commodity hardware PCs. Two different event builder protocols have been implemented and compared. Comparison with an event builder based on a implementation of Virtual Interface Architecture (M-VIA) are also presented. Future plans for larger systems are also included.

Presentation:  Adobe Acrobat pdf Short Paper:  Adobe Acrobat pdf 

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