The NA48 event-building PC farm

The NA48 experiment at the CERN SPS aims to measure the parameter R epsilon (epsilon'/epsilon) of direct CP violation in the neutral kaon system with a n accuracy of 2 x 10(-4). Based on the requirements of: high event rates (up to 10 kHz) with negligible dead time support for a variety of detectors with very wide variation in the number o f readout channels data rates of up to 150 MByte/s sustained over the beam burst. level-3 filtering and remote data logging in the CERN computer center the collaboration has designed and built a modular pipelined data how syste m with 40 MHz sampling rate. The architecture combines custom-designed comp onents with commercially available hardware for cost effectiveness and flex ibility. To increase the available data bandwidth and to add filtering and monitorin g capabilities, the original custom-built event builder hardware has been r eplaced by a farm of 24 Intel PentiumII based PCs running the Linux operati ng system during the shutdown between the 1997 and 1998 data taking periods . During the data taking period 1998 the system has been successfully opera ted taking ca. 70 Terabyte of data.