A standard snapshot notification framework in Linux ?

A standard snapshot notification framework in Linux ?

[Block Device]

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
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

Re: A standard snapshot notification framework in Linux ?

[Coywolf Qi Hunt]

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