Talk:RAID, performance tests

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Equipment:

Athlon X2 5000+ 
    3x Western Digital 250GB drives (WDC WD2500JS-22NCB1 10.02E02 SATA-300)
    2x Western Digital 500GB drives (WDC WD5000AAKS-00YGA0 12.01C02)
    Nvidia nForce onboard RAID controller, Promise TX2300 RAID controller

Athlon 64 3500+ 
    5x Seagate 750GB drives (Seagate ST3750640NS 3.AEE SATA-150)
    Nvidia nForce onboard RAID controller

Procedure:

/usr/bin/time -h measuring simultaneous cp of 3.1GB files to /dev/null
    files generated with dd if=/dev/random bs=16M count=200
    simultaneous cp processes use physically separate files
write performance tested with dd if/dev/zero bs=16M count=200
sysctl -w vfs.read_max=128 unless otherwise stated

Notes:

system default of vfs.read_max=8
bonnie++ was flirted with, but couldn't figure out how to make it read 
  big enough chunks of data to ever once hit the disk instead of the cache!

Ancillary data:

write performance (1 process)
5 250GB/500GB, graid3               : 153 MB/s
5 250GB/500GB, graid3 -r            : 142 MB/s
1 500GB drive                       :  72 MB/s
1 WD Raptor 74GB drive (Cygwin)     :  60 MB/s
1 250GB drive                       :  58 MB/s
5 250GB/500GB, gmirror round-robin  :  49 MB/s
5 250GB/500GB, gmirror split 128k   :  49 MB/s

1 process
5 250GB/500GB, graid3               : 213 MB/s (dips down to 160MB/sec)
5 750GB disks, graid3               : 152 MB/s (wildly fluctuating 120MB/s-200MB/s)
3 250GB disks, graid3               : 114 MB/s (dips down to 90MB/sec)
1 500GB disk                        :  76 MB/s
1 750GB disk                        :  65 MB/s (60MB/s-70MB/s)
5 250GB/500GB, gmirror round-robin  :  63 MB/s
3 250GB disks, gmirror round-robin  :  59 MB/s
1 250GB disk                        :  56 MB/s (very little variation)
3 250GB disks, gmirror split 128K   :  55 MB/s
5 250GB/500GB, gmirror split 128K   :  54 MB/s

2 processes
5 250GB/500GB, graid3               : 128 MB/s (peak: 155+ MB/sec)
5 750GB disks, graid3               : 125 MB/s (peak: 140+ MB/sec)
3 250GB disks, graid3               :  98 MB/s (peak: 130+ MB/sec)
3 250GB disks, graid3 -r            :  88 MB/s (peak: 120+ MB/sec)
2 250GB disks, nVidia onboard RAID1 :  81 MB/s (peak: 120+ MB/sec) // initial test had flawed data - retested for final article
5 250GB/500GB, gmirror round-robin  :  73 MB/s
2 250GB disks, Promise TX2300 RAID1 :  70 MB/s (peak: 100+ MB/sec) // initial test had flawed data - retested for final article
1 500GB disk                        :  70 MB/s
1 250GB disk                        :  56 MB/s (peak: 60+ MB/sec)
2 250GB disks, gmirror round-robin  :  55 MB/s (peak: 65+ MB/sec)
3 250GB disks, gmirror round-robin  :  53 MB/s
5 250GB/500GB, gmirror split 128K   :  50 MB/s
3 250GB disks, gmirror split 128K   :  46 MB/s

3 processes 
5 250GB/500GB, graid3               : 106 MB/s (peak: 130+ MB/sec low: 90+ MB/sec)
5 250GB/500GB, graid3 -r            : 103 MB/s (peak: 120+ MB/sec low: 80+ MB/sec)
1 500GB disk                        :  72 MB/s
5 250GB/500GB, gmirror round-robin  :  69 MB/s
1 250GB disk                        :  55 MB/s
3 250GB disks, gmirror round-robin  :  53 MB/s
3 250GB disks, gmirror split 128K   :  49 MB/s
5 250GB/500GB, gmirror split 128K   :  47 MB/s

4 processes
5 250GB/500GB, graid3               : 105 MB/s (peak: 130+ MB/sec low: 90+ MB/sec)
5 250GB/500GB, graid3 -r            : 105 MB/s (peak: 120+ MB/sec low: 80+ MB/sec)
1 500GB disk                        :  72 MB/s
5 250GB/500GB, gmirror round-robin  :  71 MB/s (peak:  75+ MB/sec low: 64+ MB/sec)
3 250GB disks, gmirror round-robin  :  65 MB/s
1 250GB disk                        :  55 MB/s
3 250GB disks, gmirror split 128K   :  55 MB/s
5 250GB/500GB, gmirror split 128K   :  47 MB/s (peak:  59+ MB/sec low: 31+ MB/sec)

5 processes
5 250GB/500GB, graid3 -r            : 107 MB/s (peak: 120+ MB/sec low: 80+ MB/sec) 
5 250GB/500GB, graid3               : 105 MB/s (peak: 130+ MB/sec low: 90+ MB/sec)
5 250GB/500GB, gmirror round-robin  :  72 MB/s (peak:  80+ MB/sec low: 67+ MB/sec)
1 500GB disk                        :  72 MB/s
1 250GB disk                        :  56 MB/s
5 250GB/500GB, gmirror split 128K   :  47 MB/s (peak: 60+ MB/sec low: 35+ MB/sec)

vfs.read_max=8, 2 parallel cp processes
3 250GB disks, gmirror round-robin : 31 MB/s
1 250GB disk                       : 27 MB/s
2 250GB disks, gmirror round-robin : 23 MB/s

Preliminary conclusions:

system default of vfs.read_max=8 is insufficient for ANY configuration, including vanilla single-drive
gmirror read performance sucks - Promise read performance sucks - nvidia read performance sucks for single-process
graid3 is the clear performance king here and offers very significant write performance increase as well
SATA-II seems to offer significant performance increases over SATA-I on large arrays