Re: incremental rbd export / sparse files?

[Wido den Hollander <wido@widodh.nl>]

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?

Wido

> sage
>
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