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Subject: Re: Adding snapshot capability to Linux
From: Xavier Bestel <xavier.bestel@free.fr>
To: Alexander Viro <viro@math.psu.edu>
Cc: Alvaro Figueroa <fede2@fuerzag.ulatina.ac.cr>,
        LKML <linux-kernel@vger.kernel.org>
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Date: 23 Apr 2002 16:58:50 +0200
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le mar 23-04-2002 ? 16:45, Alexander Viro a ?crit :
> You _can't_ get consistent snapshots without cooperation from fs.  LVM,
> EVMS, whatever.  Only filesystem knows what IO needs to be pushed to
> make what we have on device consistent and what IO needs to be held
> back.  Neither VFS nor device driver do not and can not have such
> knowledge - it depends both on fs layout and on implementation details.

I always thought that with a journalled fs, data was always consistent
on disk - i.e. always in a state where remounting the image (and
replaying the journal) makes it consistent.


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