pvmove: Reduce LV first.

redhat.com | Red Hat, Inc.: "> % pvmove /dev/sdb
> No extents available for allocation
>
> I'm assuming that this means that there's nowhere to move the data that
> is on /dev/sdb. I further assume this means that I need some free
> physical extents somewhere. This is where I'm confused. When I set up
> LVM, I allocated all of my spare drives to it. So I have a 271GB
> logical volume of which I'm using only 32GB. So I know that I have free
> space to move the data around; I just don't know how to do it.

Your logical volume is 100% used by the filesystem. It sounds like the
filesystem isn't full though, but LVM doesn't know that.

You need to shrink your filesystem, then shrink your LV, then use
pvmove."