I just upgraded to 3.8-4. I made a new RAID1 pool with three disks and discovered that the pool got created as Single. I tried several times to make a RAID1 pool using two and three disks and it was always created as Single. The reported free space was consistent with an actual Single pool so it’s not an instrumentation error.
I next tried to create a Single pool with sda and changed its level to RAID1 by adding sdb to it, and it seemed to succeed until I refreshed the pool details page. sda was no longer a member of the pool and sdb was the only member of the pool, which was now Single.
I finally tried to make a RAID5 out of the three disks and it seemed to be successful.
Right now I can’t make a RAID1 pool in any way I can find.