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

Tony Arnold tony.arnold at manchester.ac.uk
Thu Nov 26 10:29:15 UTC 2015


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

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

Thanks once again.

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 at manchester.ac.uk

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