[linux-lvm] pvmove to smaller PVs

[Dieter Stüken]

Alasdair G Kergon wrote:
> On Wed, Apr 05, 2006 at 07:34:18PM +0200, Fredrik Tolf wrote:
>> Can pvmove not just divide that storage into three "partitions", 
> 
> There's no logic to do that yet.  It can only move complete sets of
> contiguous extents.
> 
>> Is there a way for me to tell it to do so?
> 
> As you found: break up contiguous extents explicitly on
> the command line by telling it to move smaller parts that it
> can handle.

I run into the same problem: I got a hw-raid controller and merged
all my individual disks into a raid5. Thus I got one big PV instead
of several small one. After moving back and forth some lvs, my PV
gets more and more fragmented. Thus I have to instruct pvmove
explicitly which fragments have to move.

The pvmove manpage explains shortly how pvmove works: Segments to
to move are added to a temporary 'pvmove' lv, but it seems lvmove
won't split any source segment into smaller pieces to fit into
any target segment. I may explicitly express source segments
(using :PE-PE), but this also becomes complicated if my source PV
is fragmented, too. Even if I do so, it is not clear to me, how
to express such a fragmented pvmove with a single command. Else
I have to perform lots of single pvmoves and have to wait for each
to become ready?

Dieter.