[mythtv-users] MythTV and LVM

Alexander Fisher alexjfisher at gmail.com
Tue Jan 31 23:30:31 UTC 2006


> > 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.

I see that your new 3ware card supports online RAID expansion :) 
Perhaps you could do a quick test when setting it up?

Alex


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