[mythtv-users] MythTV and LVM

[Jarod Wilson]

On Tuesday 31 January 2006 10:06, Alexander Fisher wrote:
> > Unless you LVM on top of RAID-1 which is what I do.  While this is
> > somewhat wasteful if you put a low value on your TV recordings, I have
> > other data which I do value and they share the LVM on RAID-1 disks in
> > different partitions.
>
> Better still might be LVM on top of md RAID-5.  The ability to grow
> software RAID-5 will soon be in the mainline linux kernel.  At least
> it should be by the time you come to add a new disk.  What I haven't
> figured out yet is whether an LVM PV will automatically see the new md
> device size.  Perhaps somebody who has grown a hardware RAID can
> answer this?
>
> If PVs and associated volume groups don't magically grow after a RAID
> reshape, all is not lost.  I think md devices can be partitioned.  In
> this situation, you would add a new partition to the md device each
> time you add a disk.  Do a pvcreate on the new partition and then a
> vgextend to include the new PV.
> Simple!  I think. :)
>
> Seriously, if somebody thinks I've got this all wrong, please speak
> up.  This is how I plan on setting up my disks when I rebuild my
> backend after 0.19 is out.

Hrm, I just had to stop and rethink something I wrote earlier. I dunno if the 
PV is automatically grown to match the new RAID5 size or not. Good 
question... I *think* since a PV maps straight to a device, which in this 
case, would be something like /dev/md0, whatever the new size of /dev/md0 is, 
the PV should take on that size, so at that point, you should be able to grow 
an LV and the file system on top of it.

-- 
Jarod Wilson
jarod at wilsonet.com
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