Re: Failed, but "md: cannot remove active disk..."

["Michał Sawicz" <michal@sawicz.net>]

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Dnia 2012-05-14, pon o godzinie 20:22 +1000, NeilBrown pisze:
> On Sun, 13 May 2012 20:21:48 +0200 Michał Sawicz <michal@sawicz.net> wrote:
> 
> > Hey,
> > 
> > I've a weird issue with a RAID6 setup, /proc/mdstat says:
> > 
> > > md126 : active raid6 sda1[3] sdh1[6] sdg1[0](F) sdf1[5] sdi1[1] sdc[8] sdb[7]
> > >       9767559680 blocks super 1.2 level 6, 512k chunk, algorithm 2 [7/6] [_UUUUUU]
> > 
> > So sdg1 is (F)ailed, yet `mdadm --remove` yields:
> > 
> > > md: cannot remove active disk sdg1 from md126 ...
> 
> There is a period of time between when a device fails and when the raid456
> module finally lets go of it so it can be removed.  You seem to be in this
> period of time.
> Normally it is very short.  It needs to wait for any requests that have
> already been sent to the device to complete (probably with failure) and
> very shortly after that it should be released.  So this is normally much less
> than one second but could be several seconds is some excessive retry is
> happening.
> 
> But I'm guessing you have waited more than a few seconds.

Yup :)

> I vaguely recall a bug in the not too distant past whereby RAID456 wouldn't
> let go of a device quite as soon as it should.  Unfortunately I don't
> remember the details.  You might be able to trigger it to release the drive
> by adding a spare - if you have one - or maybe by just
>   echo sync > /sys/block/md126/md/sync_action
> it won't actually do a sync, but it might check things enough to make
> progress.

# echo sync > /sys/block/md126/md/sync_action
-bash: echo: write error: Device or resource busy

eh?

> What kernel are you using?

# uname -a
Linux media 2.6.38-gentoo-r6 #2 SMP Tue Sep 13 19:13:42 CEST 2011 x86_64
AMD Athlon(tm) 64 X2 Dual Core Processor 4200+ AuthenticAMD GNU/Linux

Thanks,
-- 
Michał Sawicz <michal@sawicz.net>

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