Consumer-server/logger system for the CDF experiment

The level-3 trigger system for the CDF experiment runs on a farm of Linux PCs. Events that pass this trigger system are collected and logged to disk by a logger process running on an SGI Origin 200 GIGAchannel server. The system must support data logging at 75 Hz for 250 KB events. In addition, some of the events are sent to remote consumer processes for online monitoring. The Consumer-server/logger system inherently behaves like an intelligent hardware hub, maintaining connectivity between these large numbers (~200) of Level-3 farm nodes, consumer processes, and the logging hardware. The farm nodes and the consumer processes are networked using multiple Fast Ethernet interfaces while the disk subsystem of 0.5-1 TB capacity is connected via dual fibre channel arbitrated loops. Different functions of the consumer-server/logger are implemented as distinct state machines to keep each section of the code as simple and robust as possible. In this paper, we describe the first implementation of the system and present initial performance results conducted at CDF