1. A Linux PC Farm for Physics Analysis at the ZEUS Experiment Marek Kowal, Krzysztof Wrona, Tobias Haas, Ingo Martens, Rainer Mankel DESY, Notkestrasse 85, Hanburg, Germany http://zarah.desy.de/

2. Marek Kowal tomcat@mail.desy.de A Linux PC farm - plan of talk Overall status Key issues Hardware and Software Next steps

3. Marek Kowal tomcat@mail.desy.de Overall status First reconstruction farm working since 1997 Right now farm consists of 47 PCs Both reconstruction and analysis software runs efficiently on PCs

4. Marek Kowal tomcat@mail.desy.de Key issues Big computing power Big IO rate Easy user interface Maintenance Prices

5. Marek Kowal tomcat@mail.desy.de Hardware - introduction “worker” PCs - 45 “server” PCs - 2 Fileservers - 3 TB Old SGI Multiprocessor machines - 44 processors Network

6. Marek Kowal tomcat@mail.desy.de PCs - commodity hardware Farm built over past three years Number of PCsprocessormemoryIDESCSI –16 BPPro 20064MB2GB- –1 SPPro 200128MB2GB3x8GB –19 BPII 350128MB6GB- –1 SPII 350256MB6GB3x8GB –10 BPIII 450128MB8GB- Each PC equipped with 100Mb network card

7. Marek Kowal tomcat@mail.desy.de Fileservers - SGI Origin 2000, 4xIP27 195MHz, 0.75GB RAM, HIPPI 800Mb, 1Gb Challenge DM, 4xIP19 100MHz, 384 MB RAM, HIPPI 800Mb SCSI discs - 2TB Fibre Channel (!) discs - 1TB

8. Marek Kowal tomcat@mail.desy.de SGI Challenge XL total of three machines total of 44 processors (IP19,IP25) /20,16,8/ 4.3GB RAM /1.5,1,1.8/ HIPPI 800Mb

9. Marek Kowal tomcat@mail.desy.de Network hardware

10. Marek Kowal tomcat@mail.desy.de Software - introduction BATCH System Job submission tpfs & RFIO WWW interface

11. Marek Kowal tomcat@mail.desy.de Batch system NQS and LSF evaluated, LSF choosen for PCs LSF –possibility to define load window –possibility to define resource requirements for job (HDD!) SGI Challenges - still NQS

12. Marek Kowal tomcat@mail.desy.de Job submission software Allows to submit jobs (binaries & data) to batch system Each job is allocated its own working directory Operations supported: submission, retreival, querying status, listing, killing, purging Avaliable for: Linux, Solaris, IRIX, OSF1, Windows NT

13. Marek Kowal tomcat@mail.desy.de tpfs tpfs - transparent access to data stored on robots (hard copy) and discs (cached copy) automatic staging of files upon trial to open them

14. Marek Kowal tomcat@mail.desy.de RFIO stateless avaliable as dynamically loaded library (DLL) > export LD_PRELOAD_PATH=librfio.so > some_program

15. Marek Kowal tomcat@mail.desy.de WWW interface queues status / steering systems’ load and statistics discs avaliability and free space reports staging status and statistics

16. Marek Kowal tomcat@mail.desy.de Maintenance & Costs More space required for PCs than for Challenges (Racks!) No real console avaliable (BIOS problems!) Synchronization of software - AFS Price: 3000DM (PC, rack space, switch port, cabling and LSF licence)

17. Marek Kowal tomcat@mail.desy.de Next steps - hardware complete removal of SGI machines except for Origin2000 fileserver further PCs to be added increase in size of discs attached to fileserver - up to 4.5 TB till the end of 2000

18. Marek Kowal tomcat@mail.desy.de Next steps - software Development of new job submission software written as JAVA applet accesible via WWW New version of RFIO software with support for Disc Cache project started at DESY (see poster session - Patrick Fuhrmann)

19. Marek Kowal tomcat@mail.desy.de Have you got any questions? …...

20. A Linux PC Farm for Physics Analysis at the ZEUS Experiment Marek Kowal, Krzysztof Wrona, Tobias Haas, Ingo Martens, Rainer Mankel DESY, Notkestrasse 85, Hanburg, Germany http://zarah.desy.de/