Date: Tue, 15 Nov 2005 16:24:08 +0800
From: Coywolf Qi Hunt <qiyong@fc-cn.com>
To: Block Device <blockdevice@gmail.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: A standard snapshot notification framework in Linux ?
Message-ID: <20051115082408.GA3249@localhost.localdomain>
References: <64c763540511142345g4ca0b184y28962dae494f22b4@mail.gmail.com>
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On Tue, Nov 15, 2005 at 01:15:54PM +0530, Block Device wrote:
> Hi,
> 
>    does the linux kernel provide a mechanism whereby applications can
> register themselves
> to be notified when a snapshot is being taken of the volume they might
> be writing to.
> 
>    If there is no such framework then how do backup applications
> guarantee ( application level ) consistency. I have seen freeze_bdev

call sync and mount read-only, or go down to init 1.

	Coywolf

> and friends which work for file systems and how the device mapper uses
> them. But when it comes to application level consistency, a mechanism
> is required to give the application a chance to flush &  quiesce its
> writes so that the backup taken will be consistent for the application
> also. Windows has the VSS ( Volume Shadow Service ) which provides an
> elaborate framework for this. Is anyone working on something similar
> for Linux and if not why is it not such a worthwhile idea ?
> 
> Regards
> BD
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