One is the UUID for the array (starting with "06ad") - this is what you
use in /etc/mdadm.conf. The second is the UUID for the filesystem you
have on the array (starting with "ceef") - that's used in /etc/fstab. If
you recreate the filesystem then you'll get a different filesystem UUID
but keep the same array UUID.

Cheers,
    Robin

Thank you Robin, this is helpful. Can you recommend some place to read
up on UUIDs and raid arrays, or some general UUID documentation?

Cheers,
Bill