Re: pvmove thin volume doesn't move

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

Dne 19. 11. 25 v 15:07 Matthew Patton napsal(a):
> <quote>
> Usually once user goes with thin-pools - it's decision taken with knowledge that the only way out is to take out whole data out of thin-pool and copy them to the new place
> </quote>
> 
> That is one hell of a wild and unsupported assumption. Practically nobody , even seasoned sysadmins would know of this deficiency. Does the lvm(1) manage splatter this warning prominently?
> 
> Pretty sure the HP/ux and IBM implementations support thin movement.

Well I've no idea which volume managers you are talking about, all I say is - 
lvm2  ATM does not support any sort of 'extraction' of a thinLV out of the 
thin-pool. The main benefit of using 'thin-pool' is the you share storage 
between volumes.

As far as for documentation - I'm pretty sure we never mentioned any support 
of such operation within our lvm2 man pages.

And the initial lines in our 'man lvmthin' explicitly states this:

----
Blocks in a standard LV are allocated (during creation) from the Volume Group 
(VG), but blocks in a thin LV  are  allocated  (during  use)
from a "thin pool".  The thin pool contains blocks of physical storage, and 
thin LV blocks reference blocks in the thin pool.

----

Thin-pool is some sort of a black box from lvm2's POV - it serves volumes - 
and lvm2 knows how to make those volumes available on the system - but the 
mapping of chunks to make a thin LV as fully in hands of thin-pool target.
lvm2 has 'no idea'  which disk space is in-use for any individual thin LV.
(there are tools like 'thin_ls/thin_rmap' for that)


Regards

Zdenek