btrfs scrub complete

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.

Speed of btrfs scrub

Here’s the output of the status command:

[root@supermario ~]# btrfs scrub status /media/Photos/
scrub status for 27cc1330-c4e3-404f-98f6-f23becec76b5
 scrub started at Tue Mar 21 17:18:13 2017, running for 01:05:38
 total bytes scrubbed: 1.00TiB with 0 errors

So on Fedora 25 with an AMD-8323 (8 core, no hyperthreading) and 24GB of RAM with this hard drive and its 3TB brother in RAID1 , it takes about an hour per Terabyte to do a scrub. (Which seems about equal to what a coworker told me his system takes to do a zfs scrub – 40ish hours for about 40ish TB)