Re: [linux-lvm] What have snapshots got to do with LVM ?

["Heinz J. Mauelshagen" <Mauelshagen sistina com>]

On Mon, Apr 23, 2001 at 09:38:18AM +0100, Joe Thornber wrote:
> On Mon, Apr 23, 2001 at 10:21:45AM +0000, Heinz J. Mauelshagen wrote:
> > On Sun, Apr 22, 2001 at 01:09:24PM +0100, Joe Thornber wrote:
> > > Just a random Sunday morning thought:
> > > 
> > > Why don't we split snapshots off into their own driver so we can
> > > snapshot any block device, putting the COW tables on any other block
> > > device ?  
> > 
> > Any other block device devides into PE similar allocation units carrying their
> > own COW exception table at the beginning?
> 
> I'm not sure I understand your comment.  There are two devices the
> snapshot origin and the snapshot storage device.  We can divide the
> snapshot storage device up how we want, the COW exception tables go in
> here.

With LVM sanpshots we devide a device into PEs, allocate parts of the
COW table dealing with exceptions stored in a specific PE at the very
beginning of the PE.

My point is, that a similar allocation policy needs to take place on a
general block device too in order to avoid disk access overhead.


> 
> - Joe
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-- 

Regards,
Heinz    -- The LVM Guy --

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen Sistina com                           +49 2626 141200
                                                       FAX 924446
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