Re: LVM vs. Ext4 snapshots (was: [PATCH v1 00/30] Ext4 snapshots)

[Christoph Hellwig]

On Wed, Jun 08, 2011 at 09:26:11PM +0300, Amir G. wrote:
> In my old next3.sf.net wiki, which I do update from time to time,
> I listed 4 advantages of Ext4 (then next3) snapshots over LVM:
> * Performance: only small overhead to write performance with snapshots
> * Scalability: no extra overhead per snapshot
> * Maintenance: no need to pre-allocate disk space for snapshots
> * Persistence: snapshots don't vanish when disk is full
> 
> As far as I know, the only thing that has changed from dm-snap
> to dm-multisnap is the Scalability.

I don't think you have looked at dm-multisnap at all, have you?  It
addresses all your points and many more.  Take a look at the code which
is in the multisnap branch of https://github.com/jthornber/linux-2.6/,
there's also some slides on it from Linuxtag at:

https://github.com/jthornber/storage-papers/blob/master/thinp-snapshots-2011/thinp-and-multisnap.otp?raw=true

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