Curtis Jones wrote:

1. is btrfs-convert on /dev/md0
stable/reliable/tested/not-a-stupid-thing-to-do? 2. based on the reading
I've done, resizing btrfs is supported. can you confirm? 3. there aren't
any known compatibility or other issues with running btrfs on top of mdadm
(raid 6) 4. any other caveats I might want to consider?

We've been running btrfs on mdadm for a year or so with no problems (it was 
a fresh file system, though).

Jeremy