A FDDI based processor farm for the ZEUS Third Level Trigger
Paper: 453
Session: B (talk)
Speaker: Polenz, Stefan, DESY, Hamburg
Keywords: ?
A FDDI based processor farm for the ZEUS Third Level Trigger
ZEUS is one of the HERA ep-collider experiments at DESY Hamburg with a
bunch crossing time of 96 nsec. The design input rate of the Third
Level Trigger (TLT) is 100 Hz at event sizes of 80 kBytes. At present
the Event Builder places the events in 3 independent VME memories.
To meet the requirements of computing power and bandwidth the
TLT is realized in multiple FDDI loops each consisting of various
Silicon Graphics Challenge S machines with FDDI SAS, one RADSTONE
VME/FDDI board as interface between FDDI and VME and a FDDI
concentrator. The FDDI loops are connected by a Network Switch which
provides network load shielding and connection to the TLT data
sink. For the data transfer between the UNIX stations and the RADSTONE
board a "reliable" UDP protocol was developed yielding a transfer rate
of 7 MB/sec. The application on the RADSTONE board is running under
the WindRivers VxWorks operating system. The event output from the
UNIX stations uses TCP/IP protocol.
The processes on the UNIX stations are well separated into 4
categories, the physics filters, the monitoring of the filters and the
control and transport layers. The process design provides easy
maintenance of the physics filter code and allows the transport
processes to be simply ported to other data transport media. The
control processes allow for self synchronization, i.e., a restarted
process can join the system during data taking.
The reliability and performance of the system over one data
taking period of 6 month will be reported.