[linux-lvm] access or interface to list of blocks that have, changed via C.O.W.?

[Stuart D Gathman]

On 10/04/2012 11:02 AM, Mark Woodward expounded in part:
>
>> snapshot target and metadata format. It does not share code with
>> current (or historic afaik) LVM2/device-mapper and has been dead for a
>> number of years (last commits around 2008).
>>
>>> get the code. It old and not supported currently, but still works.
>>> I
>> Really? I'd be surprised if it even builds against modern kernels or
>> device-mapper.
> ddsnap was the Zumastor snapshot tool which uses a different in-kernel
> Well.....
> The LVM2 code that ships with most distros still uses the old 
> interfaces and still (Ubuntu 12.04) seemst to create a COW file with SnAp

This utility (ddsnap work alike) requires no kernel changes, and only 
depends on the layout of the COW (and only on the changed block table):

http://www.opensvc.com/init/default/doc_storage_dds