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

Bryn M. Reeves bmr at redhat.com
Tue Dec 9 18:06:24 UTC 2008

Kai Schaetzl wrote:
> Stuart D. Gathman wrote on Tue, 9 Dec 2008 11:54:08 -0500 (EST):
> Hallo, thanks for the suggestions. I'll try to follow that logically and with 
> possible commands, see below with comments/questions.
>> 1) remove sda from md2 array
> mdadm /dev/md2 --fail /dev/sda3 --remove /dev/sda3
>> 2) use dd or pvremove to clear PV info in md2.  This should not
>>    affect sda since sda is removed from md2
> md2 shouldn't have PV info. do you mean sdb3? (this would destroy my data on 
> sdb3 then), so:

Are you sure? If the MD array is a straightforward RAID1 mirror of two 
SD devices then the PV data should also be visible on the MD device - 
see my other post.

> vgchange dom0 -an (deactivate the LVs on sdb3)
> pvremove /dev/sdb3 ?
> After this point a pvdisplay should show /dev/sda3 as the active PV for dom0.
> (At the moment I get: "using /dev/sdb3 not /dev/sda3")
>> 3) pvcreate md2 as a new PV and add to volume group
> pvcreate /dev/md2
> I fear I will get "device busy", not? (just a feeling from recent experience 
> with juggling with md and lvm that are on top of each other)
> vgextend dom0 /dev/md2
> (dom0 then consists of sda3 and md2)

If there are still active LVs (or if the LVM2 tools recognise md2 as a 
PV) then you will get an error here - either that the device could not 
be opened exclusively (LVs present) or that you can't initialise the new 
PV without '-ff' as it is already part of a volume group.


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