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COMPASS

COMPASS. Comp uterized A nalysis and S torage S erver Iain Last. Outline. Why? Hardware Linux Device Drivers Linux Installation and Limits Benchmarking Tests Results Future. Why?. Store all the data on disk rather than tape. Faster access to data than with tape.

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COMPASS

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  1. COMPASS Computerized Analysis and Storage Server Iain Last

  2. Outline • Why? • Hardware • Linux Device Drivers • Linux Installation and Limits • Benchmarking Tests • Results • Future Iain Last, University Of Liverpool

  3. Why? • Store all the data on disk rather than tape. • Faster access to data than with tape. • Run jobs on server containing data. Iain Last, University Of Liverpool

  4. Hardware • Dell PowerEdge Server, 450 MHz Pentium III, 256 Mb RAM with 4 internal SCSI disks. • 4 PowerVault 1200 Disk Servers each with 8 Ultra Wide SCSI LVD disks.Total > 1Tb disk space • Adaptec Ultra Wide SCSI cards. Iain Last, University Of Liverpool

  5. Linux Devices Drivers • Linux Device Drivers: • Devices accessed through special files in /dev directory specifying block or character device and major / minor number pairs. • Major number refers to a device driver e.g. 8 is a SCSI disk (see /usr/src/linux/include/linux/major.h) • For disks, minor number refers to disk / partition on disk e.g. /dev/sda major:8 minor:0 first SCSI disk found on system /dev/sda1 major:8 minor:1 first partition /dev/sda15 major:8 minor:15 last partition on first disk /dev/sdb major:8 minor:16 second SCSI disk found on system • minor numbers are 8-bit i.e. only have values in range 0-255 only 16 disks per disk major number. Iain Last, University Of Liverpool

  6. Linux Installation & Limits • RedHat Linux 5.2: Kernel 2.0.x • Used at Liverpool and CERN – problem: only one SCSI major number is defined – maximum of 16 SCSI disks allowed. • Kernel “hacking” necessary to register new SCSI major number with system. • RedHat Linux 6.0: Kernel 2.2.x • Defines 8 SCSI major numbers : 8, 65-71- max. 128 SCSI disks. • Have to create some special files in /dev by hand – relatively trivial with mknod • Physical limit of only 4 PCI slots for SCSI cards on motherboard Iain Last, University Of Liverpool

  7. Benchmarking Tests • Use CERN sequential IO tests for read / write / calibration. • Calculates average write rate over previous 10 writes • Calibration: Comment out write statement and run write tests again. • Read test averages file read for > 10Mb data over previous 10 reads. • Modified version of above calculates averages over the whole file. Iain Last, University Of Liverpool

  8. Results: Writing I Iain Last, University Of Liverpool

  9. Results: Writing II Iain Last, University Of Liverpool

  10. Results: Reading Iain Last, University Of Liverpool

  11. Future • Have a 32/64 bit PCI Copper Duplex / Optical Fibre Channel RAID disk to test. • More work needed to understand Linux timings and IO. Iain Last, University Of Liverpool

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