Re: RAID5 check does not read disk media

[NeilBrown <neilb@suse.de>]

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On Wed, 4 Apr 2012 14:51:52 +0100 Mathias Burén <mathias.buren@gmail.com>
wrote:

> On 4 April 2012 14:23, Peter Urbanec <linux-raid@urbanec.net> wrote:
> > I'm running Gentoo kernel 3.3.0 with raid5 on four ICH7 AHCI connected
> > Seagate 2TB 7200RPM disks. I also have two WD 1TB Green disks in raid1 on a
> > Sil3114 with a JBOD (non-RAID) BIOS.
> >
> > When I attempt to do a scrub/check on the raid5, the check seems to proceed
> > without actually reading any data from the disks - the disk activity lights
> > do not even flicker.
> >
> > Looking at the speed at which the check completes confirms this:
> >
> > # cat /proc/sys/dev/raid/speed_limit_min
> > 10000
> > # cat /proc/sys/dev/raid/speed_limit_max
> > 4000000
> > # echo check > devices/virtual/block/md0/md/sync_action
> > # echo check > devices/virtual/block/md127/md/sync_action
> > ...
> > # cat /proc/mdstat
> > Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
> > md127 : active raid1 sdf1[1] sde1[0]
> >      976760384 blocks [2/2] [UU]
> >      [>....................]  check =  1.7% (17387072/976760384)
> > finish=380.7min speed=41994K/sec
> >
> > md0 : active raid5 sdb[1] sda[0] sdd[4] sdc[2]
> >      5860535808 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4]
> > [UUUU]
> >      [==================>..]  check = 93.9% (1835359616/1953511936)
> > finish=0.8min speed=2332893K/sec
> >
> >
> > raid1 runs at about 42MB/s as expected with two WD 1TB Green drives.
> > raid5 runs at well over 2GB/s - not really possible with four Seagate 2TB
> > 7200RPM drives.
> >
> > Any ideas on what may be going on there and how to fix it. Let me know
> > what/if more information may be needed.
> >
> > Thanks
> >
> >    Peter Urbanec
> >
> > --
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> 
> FWIW I'm seeing this as well, kernel 3.3.1, but on RAID6. There's a
> message just a few days about this, but no link to a patch.

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=c6d2e084c7411f61f2b446d94989e5aaf9879b0f

NeilBrown

> 
> Mathias
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
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