This was the status at the end of the scrub:
[root@supermario ~]# /usr/sbin/btrfs scrub start -Bd /media/Photos/ scrub device /dev/sdd1 (id 1) done scrub started at Tue Mar 21 17:18:13 2017 and finished after 05:49:29 total bytes scrubbed: 2.31TiB with 0 errors scrub device /dev/sda1 (id 2) done scrub started at Tue Mar 21 17:18:13 2017 and finished after 05:20:56 total bytes scrubbed: 2.31TiB with 0 errors
I’m a bit perplexed at this information. Since this is a RAID1, I would expect it to be comparing info between disks – is this not so? If not, why? Because I would have expected both disks to end at the same time. Also, interesting to note that the 1TB/hr stopped being the case at some point.