XFS appears to cause strange hang with md raid1 on reboot

[Stefan Ring]

> So the filesystems are unmounted....
>
> And this says the filesystem is still mounted. Why?

When I last had a problem with shutdown, it was because of mount
namespaces. You can unmount all day long, but as long as there is a
mount still open in a namespace, nothing will get unmounted. This was
on Fedora though; don't know if RHEL 5.x makes use of namespaces.