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OffLine Physics Computing

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Presentation on theme: "OffLine Physics Computing"— Presentation transcript:

1 OffLine Physics Computing
Simulation : CPU intensive, very low I/O, very long runs Reconstruction : CPU intensive, moderate I/O, long runs Data analysis : CPU intensive, High I/O, long runs Interactive Analysis : CPU intensive, High I/O, quick response, short 10 mins intervals Tape storage : tapes in vault Staging model Traditionnally done on Mainframes (CRAY, IBM's) Simulation Recontruction Batch Data analysis Interative analysis

2 Applications Characteristics
High data volumes : tapes in vault Staging model for Data analysis (i.e, xfer tape to disk, process it, xfer it out to tape) Standard I/O package (Zebra, EPIO) Little sharing, sometime for stage input Yes, FORTRAN ! High data volumes (disks, tapes, tape robots) Standard I/O packages Little file sharing Fortran

3 SHIFT Motivations Exploit cheap RISC technology spin-off
RISC technology : 1988, Apollo DN1000 DN10000 : Mainframe CPU capacity 4-cpu, 1000 $/MIPS, 1 OS DN 10000: Faster than a mini, comparable to a mainframe SCSI disk today : > 2GB/disk, 1.8 MB/sec, < 4 K$ 3480 SCSI (STK): 2 MB/sec, 12 K$ HEP computing : always bigger needs in both data volumes CPU needs I/O bandwith SHIFT == cost effective computing SHIFT Motivations Exploit cheap RISC technology spin-off Exploit cheap SCSI technology Exploit HOPE success Answer to HEP computing always growing needs

4 SHIFT Goals Mainframe quality Scalable (down & up)
Mianframe quality: stable, resilient Scale down (small experiments, external institutes - e.g. China) Scale up (higher demand, e.g. 40 GB at design, 250 now) Heterogeneous because of economics Integrated: present 1 single view to applications, all disk & tapes available everywhere System dev ; portable to minimize efforts, adaptable to new OS, devices, HW (i.e. Unix based) Mainframe quality Scalable (down & up) Heterogeneous (open) Integrated Minimal (portable) SW development

5 SHIFT Model Split in functional blocks
Interconnect with a High speed backplane Simulation showed that for a 100 CERN Unit system : for 1 CU required 20 KB/s the backplane needed 18 MB/s + 3 MB/s Tape I/O per I/F > FDDI (at that time) & would require a lot of CPU time for protocol processing ==> UltraNet (1 Gb/s, 3-12 MB/s perf I/F) + Software !! CPU Server CPU Server CPU Server CPU Server CPU Server CPU Server Disk Server Disk Server High Speed Interconnect Tape Server Tape Server Tape Server

6 SHIFT Software Pseudo Distributed File System Tape Access Batch queues
Pseudo distributed to present one single vies Tape access at the tape file level assuming a tape staging model Batch queues system wide available (actually load balanced) Pseudo Distributed File System Tape Access Batch queues

7 SHIFT Software Disk Pool Manager Remote Tape Copy
DPM to organize file in pools of file systems (local & remote) RTCOPY = generalized remote tape staging NQS : load balancing RFIO: exploit netowrk I/O packages: Zebra, EPIO, Fatmen Developed in 4 month Currently lines of code Publicly available Disk Pool Manager Remote Tape Copy Clustered Batch Queues Remote File I/O Integration with I/O packages Unix Tape Control System Operator Interface Monitoring

8 CORE This is the environment CSF is the low I/O high CPU facility
PIAF is being integrated Link to PARC Link to CHEOPS Link to private Simul farms (Opal) Intentions to expand to all LEP experiments and prepare LHC

9 CPU usage CORE is the main CPU provider
IBM is still a big one (but $/mips) Cray is outragously expensive) IBM is still GP, CORE, SHIFT not Still have a lot to learn from mainframe world : Resilience (Disk failure rates) Maintainability (checkpoint/restart) Performance tuning Failure analysis Week

10 SHIFT Stage statistics
But after all, we do stage data, and not a little bit Tape drive usage is not bad Week Gigabytes SUN/STK stage data/drive/week : 48 GB

11 Tape mount statistics 10 % of all tape mounts ... but with 2 drives
Week 10 % of all tape mounts ... but with 2 drives We are increasing number of drives which are limiting data annalysis (jobs are waiting idle for tape mounts Tape mount/drive as good as mainframe IBM Mounts/Drive/Week SUN/STK Mounts/Drive/Week 253

12 Conclusions RISC + SCSI cost effective CSF style easy to solve
not tight to 1 manufacturer for CPU Network is not important apart speed, only the abstraction matters (sockets) Simulations : evry major HEP has such a project I/O: very few people have tried this, it caused us gey hairs Administration: machine number increase , config example, monitoring Scalable up (e.g. 40 GB to 250, DP) and down (Aleph, IHEP, SMC) Ready for LHC challenges (one order of magnitude) Only starting with // interactive data analysis Conclusions RISC + SCSI cost effective CSF style easy to solve (Remote) I/O is the major problem Administration is complex Really scalable


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