Hi Neil So, a little while ago I did upgrade the kernel (2.6.22.18-0.2-default), but it did not seem to make any difference to the 'echo sync > /sys/block/md3/md/sync_action'. After receiving your latest email, I did the following... echo sync > /sys/block/md3/md/sync_action (device busy reported to konsole as before) echo idle > /sys/block/md3/md/sync_action echo sync > /sys/block/md3/md/sync_action (device busy reported to konsole as before) Then checked "top" - and saw significant activity from md3_sync and md3_raid5 processes. Also cat /proc/mdstat showed that a resync was actively happening, and sure enough, after a couple of hours I now have 4 active devices in the array! So I suspect a combination of the new kernel and the "idle" sorted the problem, whatever it was. Thanks! And thanks for writing mdadm and for your support. Jon B NeilBrown wrote: > On Wed, July 2, 2008 4:37 am, Jon Buckingham wrote: >> Hi Neil - any thoughts on how I can debug/fix this? > > Sorry for the slow responses - I seem to have been very busy lately. > > No, unmount isn't needed. > I cannot really imagine what is happening. > Maybe write "idle" to the sync_action file first, then try > "sync", but that seems unlikely. > > Maybe unmount, stop the array, > echo 0 > /sys/modules/md-mod/paramters/start_ro > and assemble that array again > mdadm -A /dev/md3 /dev/sd[abcd]4 > and see if that helps. > > Maybe try a newer kernel if that is an option. > > NeilBrown > >> Thanks >> >> Jon B >> >> -------- Original Message -------- >> Subject: Re: mdadm: spare rebuilding >> Date: Sat, 28 Jun 2008 20:42:56 +0100 >> From: Jon Buckingham >> Reply-To: jbuckingham@blueyonder.co.uk >> To: Neil Brown >> CC: linux-raid@vger.kernel.org >> References: <48615EE7.7000502@blueyonder.co.uk> >> <18532.47293.808234.949005@notabene.brown> >> >> Neil Brown wrote: >>> Maybe a bug that has since been fixed. >>> What happens if you >>> echo sync > /sys/block/md3/md/sync_action >>> ?? >>> >> nas:~ # echo sync > /sys/block/md3/md/sync_action >> -bash: echo: write error: Device or resource busy >> >> Should I unmount first? >> Any other info? >> >> Thanks >> >> Jon B >> >> >> > > >