Am 24.11.2012 um 01:04 schrieb Wido den Hollander <[email protected]>:

> 
> 
> On 11/23/2012 05:59 AM, Sage Weil wrote:
>> On Thu, 22 Nov 2012, Stefan Priebe - Profihost AG wrote:
>>> Hello list,
>>> 
>>> right now a rbd export exports exactly the size of the disk even if there is
>>> KNOWN free space. Is this inteded to change?
>>> 
>>> Might it be possible to export just differences between snapshots and merge
>>> them later?
>> 
>> We were just talking about this the other day.
>> 
>> Step 1 is to create a mechanism to output a list of block ranges that
>> have/have not changed between snapshots.
>> 
>> Step 2 is to export the incremental changes.  The hangup there is figuring
>> out a generic and portable file format to represent those incremental
>> changes; we'd rather not invent something ourselves that is ceph-specific.
>> Suggestions welcome!
> 
> I'm not sure about the licensing and such, but doesn't VMware do something 
> with their VMDK images?
> 
> There you have a base image and each snapshot is a separate file.
> 
> You have:
> 
> image.vmdk
> image-delta1.vmdk
> image-delta2.vmdk
> ..
> ..
> 
> You can merge all these files together again to a new image based on the last 
> snapshot you feeded it.
> 
> They probably didn't use a open format to do this, but something in that 
> direction is what you are looking for?

Yes something like that would be perfect.

Stefan

> 
> Wido
> 
>> sage
>> 
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