[linux-lvm] shift PV from disk to raid device?

Kai Schaetzl maillists at conactive.com
Tue Dec 9 13:09:26 UTC 2008

Bryn M. Reeves wrote on Tue, 09 Dec 2008 10:30:54 +0000:

I notice that I wrote "/dev/sda" where I should have written "/dev/sda3", 
of course. But I guess this doesn't make a difference.

> pvmove

thank you. I remember this command from reading the LVM how-to some months 
ago, but had forgotten by now. I had checked the pvchange command, but not 
this one. After reading man pvmove I'm not sure if using that would really 
be helpful. If I understand correctly using it will still copy a lot of 
data (all the data on the LVs). Basically it seems to move out all data 
from dev/sdan to a temporary lv, then move them back in to /dev/mdn. From 
my non-expert view this might create a quite "unfavorable" data layout as 
it is all happening within the same "data location" on the disk. And all 
in all it might also take longer than a brute-force approach. I had hoped 
there's some way to just move lvm metadata so that it knows it belongs to 
/dev/mdn and not /dev/sdan anymore.
So, I wonder if it isn't as good or even better if I do the following:

- break the raid array md2 
   (made from /dev/sda3 and /dev/sdb3 with duplicate PVs)
- remove the PV on /dev/sda3
- recreate it and all LVs on /dev/md2
- copy over the data from the LVs on /dev/sdb3



Kai Schätzl, Berlin, Germany
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