Re: Slow reconstruction

[John Rowe <rowe@excc.ex.ac.uk>]

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