Belle DAQ system upgrade at 2001

Abstract We renewed the data acquisition system for the Belle experiment. Previous data acquisition system, which has been used since December 1998, did not have level 2 trigger facility. To improve the data reduction factor and total throughput, we replaced event builder, online computer farm and the storage system. The event builder and online computer farm are unified into one system. This event building farm uses commodity hardware and newly appended level 2 trigger functionality. This data acquisition system started its operation since last autumn and is very stable. We took 36 fb −1 with new DAQ system, it had already overtaken 30 fb −1 that is total amount of previous DAQ system.