[mythtv] Problems with using LVM for large storage

[Robert Kulagowski]

> This is actually a straightforward procedure and can be done with your
> system up and running. I recently had a disk in my LVM began to fail and
> I needed get all of the data off of it. I connected another drive and
> added it to the volume group (pvcreate followed by vgextend). Then I got
> the LVM to move all of the data off of the bad drive (pvmove) and then
> dropped that drive from my volume group (vgreduce). I was able to do all
> of this with the filesystem live, mounted and in use.

The last time I needed to do something like this pvmove would only work 
if the new drive that was added was the same size or larger than the one 
failing.  So adding 2 80GB drives to rescue the data from one failing 
120GB drive didn't work.  Sure, I could have done fancy tricks like 
RAID0'ing the 80GB drives then adding _that_, but the complexity would 
have made things even harder to fix later on if there were issues.