Re: pvmove thin volume doesn't move

[Zdenek Kabelac <zdenek.kabelac@gmail.com>]

Dne 19. 11. 25 v 18:38 Brian J. Murrell napsal(a):
> On Wed, 2025-11-19 at 18:31 +0100, Zdenek Kabelac wrote:
>>
>> I've been also thinking - that adding support of 'dumb' mirroring of
>> thinLV
>> into pvmove - isn't a very difficult request - so we will see -
>> although
>> obviously copying  10TiB empty thin volume isn't going to be 'a fast
>> operation' this way - but it's not any worse then a 'dd'.
> 
> Not any worse than 'dd' would be more than acceptable.  How can
> anything be faster at physically moving data than dd as it is usually
> only slowed by the speed of the storage in any case?

If the tool would have known 'which areas' are  mapped  (which knows thin-pool 
target internally) then it would need to copy only those blocks.
(this can be just small fraction of the hole volume size)

On a device level - we see 'just' zero areas - but those need to be mirrored - 
as on this level there no difference between 'zero' and 'unwritten' data.

(Btw with this knowledge the Joe's  blk-archive tools is working)

Zdenek