From: Daniel Phillips <phillips@phunq.net>
To: Andreas Dilger <adilger@sun.com>
Subject: Re: [RFD] Incremental fsck
Date: Sat, 12 Jan 2008 15:55:53 -0800
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Cc: Alan <alan@clueserver.org>, Al Boldi <a1426z@gawab.com>,
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On Wednesday 09 January 2008 01:16, Andreas Dilger wrote:
> While an _incremental_ fsck isn't so easy for existing filesystem
> types, what is pretty easy to automate is making a read-only snapshot
> of a filesystem via LVM/DM and then running e2fsck against that.  The
> kernel and filesystem have hooks to flush the changes from cache and
> make the on-disk state consistent.
>
> You can then set the the ext[234] superblock mount count and last
> check time via tune2fs if all is well, or schedule an outage if there
> are inconsistencies found.
>
> There is a copy of this script at:
> http://osdir.com/ml/linux.lvm.devel/2003-04/msg00001.html
>
> Note that it might need some tweaks to run with DM/LVM2
> commands/output, but is mostly what is needed.

You can do this now with ddsnap (an out-of-tree device mapper target) 
either by checking a local snapshot or a replicated snapshot on a 
different machine, see:

    http://zumastor.org/

Doing the check on a remote machine seems attractive because the fsck 
does not create a load on the server.

Regards,

Daniel
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