More pvmove questions...

[Stuart Abramson]

We are looking at doing some volume changes. We're considering pvmove and lvextend mirroring.

Is there risk with pvmove? What happens if the "pvmove" gets interrupted by system crash/hang? See this link:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=893310

Can you kill a pvmove in the middle and start over?

Does it release the PEs as it goes or does it release the PEs when it's done?

Can you pvmove more than one PV in a VG or does it lock the entire VG when it executes?

[Patrick Wallek · Accepted solution]

If a pvmove dies, then you do run a risk of having problems as seen in the thread you reference.

A pvmove works basically by mirroring the LV to the new location and then reducing the mirror from the old location. If I recall correctly, the PEs are not freed up until the pvmove actually finishes.

No you can't run more than 1 pvmove at a time. Since it uses mirroring, it locks the entire VG.

If you have the space, I would go with the 'lvextend -m 1' to the new location and then 'lvreduce -m 0' off the old location. I think that would be a lot safer.

[Stuart Abramson]

Patrick:

I agree with you on lvextend mirroring. It seems safer.

However, I'm watching the pvmoves as they go, and doing pvdisplays on the target PV, and I see the PE counts changing as they go.

I'm going to launch some in parallel to see what happens, but I believe that you're right on that also.

Stuart

[Bernhard Mueller]

Stuart,

as you have noticed the pe count changes while pvmove goes on.

if you kill pvmove before the move is done you will see some extents already on the target and for the rest all *mirrored* extents on the source (more extents than physically available on source pv!).

then you will have to remove (lvextend -m 0) the leftover mirror extents on the source and can start a new pvmove to finish the move.

Regards,
Bernhard