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Re: XFS filesystem corruption

To: xfs@xxxxxxxxxxx
Subject: Re: XFS filesystem corruption
From: Martin Steigerwald <Martin@xxxxxxxxxxxx>
Date: Tue, 12 Mar 2013 10:57:51 +0100
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, Julien FERRERO <jferrero06@xxxxxxxxx>, Ric Wheeler <rwheeler@xxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130307232214.GY23616@dastard>
References: <CAPcwv6wZJSBtgF-L6KNSn6N6Y+wUZJFXdbcg+zYRwoaB2sDdjw@xxxxxxxxxxxxxx> <CAPcwv6wK7m5UbJZass5690N5UpXEMV+HVzJa5mn9KWtT9UPQ9w@xxxxxxxxxxxxxx> <20130307232214.GY23616@dastard> (sfid-20130308_003651_720717_B9D6B992)
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Am Freitag, 8. März 2013 schrieb Dave Chinner:
> On Thu, Mar 07, 2013 at 02:15:31PM +0100, Julien FERRERO wrote:
> > > We actually test brutal "Power off" for xfs, ext4 and other file
> > > systems. If your storage is configured properly and you have
> > > barriers enabled, they all pass without corruption.
> > > 
> > > What hardware raid cards can do is to hide a volatile write cache.
> > > Either on the raid HBA itself or, even worse, on the backend disks
> > > behind the card. S-ata disks tend to default to write cache enabled
> > > and need to be checked especially careful (sas drives tend to be
> > > write cache disabled by default).
> >
> > 
> >
> > Write cache is supposed to be disabled on the H/W RAID (according to
> > hdparm) and barrier are correctly enabled since xfs does not report
> > any warning at mount.
> >
> > 
> >
> > The odd thing is we never see this with kernel 2.6.18 where barriers
> > weren't yet available.
> Yes they were. XFS had barrier support added in 2.6.15.

I thought this was 2.6.16? Or was that the kernel where it became usable due 
to the generic write barrier part being merged while the XFS one was ready 

I still remember the XFS filesystem crashes I had back then that went away 
with disabling the write cache of the drive in my ThinkPad T42 back then and 
where solved with 2.6.17, whereas solved a directory corruption 
issue introduced with 2.6.17. Thus I always recommended at least in 
case of write barrier usage with XFS.

Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7

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