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Re: Oops - XFS mount after replacing wrong RAID5 drive

To: linux-xfs@xxxxxxxxxxx, linux-raid@xxxxxxxxxxxxxxx
Subject: Re: Oops - XFS mount after replacing wrong RAID5 drive
From: Andrew Klaassen <ak@xxxxxxx>
Date: Mon, 5 Nov 2001 11:22:50 -0500
In-reply-to: <1004974636.7318.5.camel@jen.americas.sgi.com>
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References: <20011105103521.A3864@dkp.com> <1004974636.7318.5.camel@jen.americas.sgi.com>
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On Mon, Nov 05, 2001 at 09:37:16AM -0600,
Steve Lord wrote:

> On Mon, 2001-11-05 at 09:35,
> Andrew Klaassen wrote:

> > I think I may have just replaced the wrong drive after a SW
> > RAID5 drive failure.
> > 
> > And then I mounted the XFS filesystem read-write.  (Doh!)
> > 
> > Can I put the old probably-good drive back into the array
> > and replace the actually-bad drive?
> > 
> > Would XFS's log replay have written enough to the array to
> > get the RAID5 hopelessly out of sync with the old
> > probably-good drive?
> > 
> > (The XFS filesystem did not unmount cleanly after the first
> > drive failure.  That's why I'm assuming that it replayed its
> > log when I mounted it after replacing the drive.)

> It will have replayed its log - and that information is now
> gone, so it is a little hard to say what state the filesystem
> is really in now.

So... mount it ro,norecovery, then run xfs_repair -n?  Or just
mount it ro,norecovery and try to grab the info we absolutely

How much is it likely to have written while replaying the log? 
(There's a reasonably good chance that it sync'd before the box
went down the first time.)

For the RAID5 people:  How much has to be written to the array
before the old probably-good drive will be useless?  What will
happen if I put it back in and it's too far out of sync?

> > How do I mount the filesystem without writing anything at
> > all to the array?

> mount -o ro,norecovery
> Even a readonly mount without the norecovery will attempt to run
> recovery.

So there's no way at all to mount the filesystem without some
writing occuring?

> Best of luck!

We've been knocking on wood this whole project, and it doesn't
seem to have done us any good.  :)

Andrew Klaassen

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