Evaluating PC Computing Farms for Data-Intensive Tasks in Experimental Physics

1. PC's as computing farms: first experiences Frédéric Hemmer http://wwwinfo.cern.ch/pdp/pc/PCRD PC's as computing farms - NCF Task Force

2. Introduction • PC “R&D” started last autumn • Goals • Establish whether PC’s can be used • for data intensive computing • in the context of NA45/NA48/Compass CDR • as a alternative to large SMP’s, CS/2’s, etc. • what are the limits • Linux and Windows/NT • Good demonstrator for LHC PC's as computing farms - NCF Task Force

3. Overall Status • Hardware (reusable) • 7 Dual PII’s @ 266 MHz • 1 Alpha PWS @ 433 MHz • 1 Sun Ultra 5 @ 270 MHz with HiPPI • 100 GB disk • Initial conclusions needed before NA48 data taking PC's as computing farms - NCF Task Force

4. Background • Catherine Charbonnier, Fabien Collin, Soren Olofsson, Bernd Panzer, Cristoph Von Praun, Jes Sorenesen • Performance (aimed at CDR for Compass) • Network performance • Disk performance • Combination PC's as computing farms - NCF Task Force

5. Network performance: Results • PC’s interconnected through 100 BaseT 3Com 3000 switch • Repeated with other H/W • Half duplex behavior • Block size does not matter • Linux uses less CPU than NT  Good unidirectional performance  Disappointing CPU consumption on NT  Disappointing bi-directional performance PC's as computing farms - NCF Task Force

6. PC to PC Network performance PC's as computing farms - NCF Task Force

7. Network performance: issues • Unexplained 0.5 MB/s observed with some eepro100 versions on PCRD hardware, but OK on PCSF • Recent DEC E'net boards with chipset > 21140 give poor performance on Linux • Surprising results PC/Alpha PC's as computing farms - NCF Task Force

8. PC/Alpha Network performance PC's as computing farms - NCF Task Force

9. Disk performance • PC’s connected to SEAGATE ST19171W using two Adaptec 2940 UW • NT needs a lot of tuning (default behavior is to swap data out!) • Block size, BIOS settings, EDO/FPM does not matter  Poor performance  Windows NT even worse  Memory bandwidth is suspected PC's as computing farms - NCF Task Force

10. Disk performance • Striping has no effect • 1 stream 2 stripes : 21 MB/s (22 max) • 1 stream 3 stripes : 21 MB/s (33 max) PC's as computing farms - NCF Task Force

11. Disk performance: issues • Memory bandwidth suspected • Need to test with LX/SDRAM • RISC PCI does not support variety of boards • Combined disk/network performance even worse : 5-6 MB/s on Linux PC's as computing farms - NCF Task Force

12. Memory bandwidth (lmbench) PC's as computing farms - NCF Task Force

13. Initial conclusions (1) • PC’s can be used for low I/O tasks • Confirmed with • Simulation on PCSF • NOMAD reconstruction on Linux • NA45 reconstruction on NT • PC’s are not adequate now as disk servers PC's as computing farms - NCF Task Force

14. Initial conclusions (2) • PC world diversity • Large choice, manufacturer independent • Difficulties • EEPRO100/Base hardware problems • DEC Tulip driver problems • IDE Master/Slave problems on some HW • VGA drivers for S3 Virge • Lilo for disk > 1024 “cylinders” • PC world changes very fast, what is true today may not be tomorrow PC's as computing farms - NCF Task Force

15. PC Technology evolution in 97 • Pentium Pro  Pentium II • 50 % raw performance increase • but 50 % cache performance reduction • SEC  new motherboards • 440 FX  440 LX (SDRAM, AGP) • Recent MB’s  embedded SCSI, E’net, VGA • 100 Mbit E’net switches standard, 1000 Mbit arriving PC's as computing farms - NCF Task Force

16. Next steps • Understand I/O bandwidth problem • Measure LX/SDRAM based PC’s • Measure low-end RISC performance on • Disk • Network (HiPPI) • Experiment with PC/HiPPI • Management aspect has not been investigated • Wake on LAN • WfM PC's as computing farms - NCF Task Force

17. Questions • Why PC’s, what benefits & drawbacks • What are the parameters • Should all components be PC’s PC's as computing farms - NCF Task Force