The B-factory computer system, which provides computing resources for the Belle experiment is in the fourth year of its operation since its March 2001 installation and has been operational for one year since its partial upgrade in March 2009. This system contains 3840 CPU cores with Intel Xeon 5460 3 GHz processors, more than 2000 disk drives (total capacity: 1.5 PB), and three high-capacity tape robotic libraries (total capacity: 3.5 PB). Because of the availability of this system, KEK is considered as a facility with one of the largest tape/disk capacities in Japan. Figure 4-4-2-1 shows the annual CPU utilization in 2009 and 3.07 PB of the 3.5 PB Tape Library was already occupied by the end of FY2009. In January 2009, one third of the CPU servers was integrated to the LCG Grid activity of the Central Information System and has been available for the LHC as well as the Belle experiment.
(from 2009 KEK annual report)