1. BESIII computing 王贻芳

2. Peak Data volume/year Peak data rate at 3000 Hz Events/year: 1*10 10 Total data of BESIII is about 2*640 TB Event size(KB)Data volume(TB) RAW12120 REC.24240 DST220 MC-Rec24240 MC-DST220 Total640

3. BESIII computing needs CPU power Storage Network System software

4. CPU power needed for data reconstruction and simulation Four times reconstructions/year Equivalent to a farm of 200 P4 1.6G Analysis needs another farm of 100 P4 1.6 G Maybe underestimated MIPS/eventEvents (10 10 ) Total CPU (MIPS) Event reconstruction 20440,000 MC simulation2001100,000 MC reconstruction 20440,000 Total180,000

5. Data type and storage media Store 3 reconstructions Virtual storage library Fast and automatic access Data typeData volume(TB)device Raw240Tape lib. Rec1440Tape lib. DST120Disk array MC-Rec1440Tape lib. ? MC-DST120Disk array

6. Tape reading/writing speed Online data recording(writing): 3000*12KB=36MBytes/s Reconstruction(reading/writing): 3000*24KB*5*2 = 760MBytes/s MC simulation ? 3000*24*2 = 152MBytes/s It is almost impossible ! We should design our software framework carefully to minimize the data size !

7. Disk read/write access speed Data Reconstruction 3000*2KB*5 = 30 MB/s MC simulation 3000*2KB*5 = 30 MB/s Analysis 40*40Mb = 200 MB/s  main building to computer center

8. Network needs From Online farm to computer center 3000*12KB = 36 MB/s A dedicated Gbps network line for safety and stability Offline farm network a bottleneck User analysis > 40 users access disk files

9. Software system Mainly based on free software CERN library based Following latest development of HEP software

10. Main bottleneck Tape reading/writing use more CPU to reduce data size Network within PC farm, main building  CC DST in main building ? Large scale storage library management Large scale PC farm: stability, scalability, management