Date: Thu, 05 Jan 2012 09:56:02 +0000 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: freebsd-stable@freebsd.org Subject: Re: gmirror not synced Message-ID: <4F0573B2.9070301@infracaninophile.co.uk> In-Reply-To: <20120104194313.GA2558@lordcow.org> References: <20120104194313.GA2558@lordcow.org>
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On 04/01/2012 19:43, Gareth de Vaux wrote:
> Hi all, I've noticed that the md5 hashes of a couple of files on
> a gmirror change when I recalculate the hashes. The output usually
> cycles between 2 hashes per file.
>=20
> I'm guessing this is because each calculation reads the file
> randomly from 1 of 2 component drives, and the files in question
> had a few bit flips during their original sync. I also assume
> this's something you have to live with for gmirror? Is removing
> and completely rebuilding the secondary drive the only thing you
> can do (which might fix these bit flips but incur others elsewhere)?
No, that's not something acceptable at all. Randomly flipping bits in
files is a really nasty failure mode.
What does 'gmirror list' tell you about the state of the gmirror? Is
there any possibility that your hardware is failing? Check the SMART
attributes of the disk in the first instance (it isn't brilliant for
picking up impending failure, but it should be pretty accurate once the
drive is actually generating errors.) Also try a few passes of
memtest86 to try and spot problems with RAM. Cleaning dust out of air
vents and heatsinks and generally making sure the machine is not
overheating is a good idea too.
Actually, first thing to do is make sure you have really good backups.
Bonus points if you have been backing everything up religiously, and can
extract a known good copy of the files in question from some of the
older ones.
Cheers,
Matthew
--=20
Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard
Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate
JID: matthew@infracaninophile.co.uk Kent, CT11 9PW
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