I did
btrfs dev stat /dev/mmcblk0p2
on both boxes. And both have the same output:
root@turris1:~# btrfs dev stat /dev/mmcblk0p2
[/dev/mmcblk0p2].write_io_errs 0
[/dev/mmcblk0p2].read_io_errs 0
[/dev/mmcblk0p2].flush_io_errs 0
[/dev/mmcblk0p2].corruption_errs 0
[/dev/mmcblk0p2].generation_errs 0
On one box I do not see those parent transid lines now. And if I understand you correctly, if numbers match, it is standard transaction ongoing and nothing harmful, right?
But second one has this in the beginning of output from “schnapps list”, followed by correct list of snapshots.
root@turris1:~# schnapps list
Warning, could not drop caches
Warning, could not drop caches
parent transid verify failed on 84262912 wanted 517972 found 514186
parent transid verify failed on 84262912 wanted 517972 found 514186
Ignoring transid failure
ERROR: child eb corrupted: parent bytenr=123633664 item=334 parent level=1 child level=2
Warning, could not drop caches
After a while it looks like:
root@turris1:~# schnapps list
Warning, could not drop caches
Warning, could not drop caches
parent transid verify failed on 123961344 wanted 518196 found 518131
parent transid verify failed on 123961344 wanted 518196 found 518131
Ignoring transid failure
Couldn't setup extent tree
Warning, could not drop caches
For btrfs scrub I assume that it will be good idea to have some good snapshot safely exported first in case that something goes wrong. So I must first do some homework. And maybe I will wait for 3.11.1 and see if it solves anything by chance.
And no, I did not have power outage for at least two months.