Thanks for all the suggestions.
/proc/sys/dev/raid/speed_limit_max had the value "10000", changing it to
200000 didn't make a difference. hdparm looks OK to me:
/dev/hdm1:
Timing buffer-cache reads: 128 MB in 1.19 seconds =107.56 MB/sec
Timing buffered disk reads: 64 MB in 3.13 seconds = 20.45 MB/sec
/dev/hdo1:
Timing buffer-cache reads: 128 MB in 1.17 seconds =109.40 MB/sec
Timing buffered disk reads: 64 MB in 3.85 seconds = 16.62 MB/sec
rsync:/root# hdparm -Tt /dev/hda4
/dev/hda4:
Timing buffer-cache reads: 128 MB in 1.15 seconds =111.30 MB/sec
Timing buffered disk reads: 64 MB in 4.31 seconds = 14.85 MB/sec
/dev/hdc4:
Timing buffer-cache reads: 128 MB in 1.16 seconds =110.34 MB/sec
Timing buffered disk reads: 64 MB in 4.79 seconds = 13.36 MB/sec
/dev/hdi3:
Timing buffer-cache reads: 128 MB in 1.16 seconds =110.34 MB/sec
Timing buffered disk reads: 64 MB in 2.73 seconds = 23.44 MB/sec
/dev/hdk1:
Timing buffer-cache reads: 128 MB in 1.16 seconds =110.34 MB/sec
Timing buffered disk reads: 64 MB in 2.72 seconds = 23.53 MB/sec
DMA is enabled for all six disks.
If it helps, here is my raidtab. I wonder a little about the 64K chunk
size on the stripe but a 128K size on the RAID5. Is this good or bad?
raiddev /dev/md0
raid-level 1
nr-raid-disks 2
chunk-size 64k
persistent-superblock 1
nr-spare-disks 0
device /dev/hda2
raid-disk 0
device /dev/hdc2
raid-disk 1
raiddev /dev/md2
raid-level 0
nr-raid-disks 2
chunk-size 64k
persistent-superblock 1
nr-spare-disks 0
device /dev/hdm1
raid-disk 0
device /dev/hdo1
raid-disk 1
raiddev /dev/md3
raid-level 5
nr-raid-disks 5
chunk-size 128k
parity-algorithm left-symmetric
persistent-superblock 1
nr-spare-disks 0
device /dev/hda4
raid-disk 0
device /dev/hdc4
raid-disk 1
device /dev/hdi3
raid-disk 2
device /dev/hdk1
raid-disk 3
device /dev/md2
raid-disk 4
Comments gratefully received.
John
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