Re: [linux-lvm] Problems creating/converting large logical volume to RAID1

[Tony Arnold <tony.arnold@manchester.ac.uk>]

John,

On 24/11/15 16:49, John Stoffel wrote:

> Can I make a suggestion to you?  Instead of trying to do the mirroring
> in LVM, build yourself an MD mirror, then layer LVM ontop of that
> instead.  You get nice seperation.
> 
> You can also take that /dev/sdb3, make it into an MD RAID1 array with
> just one device, add it into the VG, then move the LVs onto the new
> device.  Once that's done, you remove the sda3 from the VG, then add
> it into the MD device.  Something like this...
> 
>> mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sdb3 missing
>> cat /proc/mdstat
>> pvcreate -v /dev/md1
>> vgextend -v vg0 /dev/md1
>> pvmove -v sda3
>> vgreduce -v vg0 sda3
>> mdadm --add /dev/md0 /dev/sda3
>> cat /proc/mdstat
> 
> And you will now be mirrored, etc.  

Thanks for your suggestion which I have now implemented. The pvmove took
a few hours (1.5TB to move!) and then also some more hours while the
mirror set synchronised. But it's all done and I now have my volumes
mirrored.

I'm still curious though why the LVM based RAID1 didn't work. I'll just
have to stay curious!

Thanks once again.

Regards,
Tony.
-- 
Tony Arnold, IT Security Analyst, University of Manchester.
T: +44 (0) 161 275 6093, F: +44 (0) 705 344 3082,
M: +44 (0) 773 330 0039, E: tony.arnold@manchester.ac.uk