Computing Power

The maximum data rate from the Belle detector, discussed in the previous section, is 15 MB/s, which corresponds to the maximum trigger rate of 500 Hz and the maximum event size of 30 KB. Raw data are accumulated at the rate of about 5 MB/s, corresponding to 400 GB/d or 80 TB/y. The traditional-style data summary tapes, DSTs, are produced from tape to tape by running the reconstruction algorithms on raw data. DSTs contain only physics events and thus the size of DST is reduced to 4 GB per pb$^{-1}$. As we have taken data of 6.8 fb$^{-1}$ between October 1999 and July 2000, we have produced 28 TB of DST. In order to satisfy the above offline computing needs, a large computing system has been set up at the computing research center of KEK. The system consists of a computing server system, a RAID disk system and tape library system for mass storage, work group servers, and high speed network systems. The network systems connect all the sub-systems. The main purpose of the offline computing system is to process data taken by the Belle detector and to store them so that users can analyze them. Fig. shows a schematic diagram of the Belle computing system. The computing server system consists of seven Ultra Enterprise servers. Each server has 28 167-MHz Ultra SPARC CPUs and is rated to be more than 7000 SpecInt92s. Each server has 7 GB of physical memory so that the parallel reconstruction processes can be run without swapping memories.

Figure: Block diagram of the Belle computing system.