On Wed, Jun 17, 2015 at 12:16:54AM -0700, Marc MERLIN wrote: > I had a few power offs due to a faulty power supply, and my mdadm raid5 > got into fail mode after 2 drives got kicked out since their sequence > numbers didn't match due to the abrupt power offs. > > I brought the swraid5 back up by force assembling it with 4 drives (one > was really only a few sequence numbers behind), and it's doing a full > parity rebuild on the 5th drive that was farther behind. > > So I can understand how I may have had a few blocks that are in a bad > state. > I'm getting a few (not many) of those messages in syslog. > BTRFS: read error corrected: ino 1 off 226840576 (dev /dev/mapper/dshelf1 > sector 459432) > > Filesystem looks like this: > Label: 'btrfs_pool1' uuid: 6358304a-2234-4243-b02d-4944c9af47d7 > Total devices 1 FS bytes used 8.29TiB > devid 1 size 14.55TiB used 8.32TiB path /dev/mapper/dshelf1 > > gargamel:~# btrfs fi df /mnt/btrfs_pool1 > Data, single: total=8.29TiB, used=8.28TiB > System, DUP: total=8.00MiB, used=920.00KiB > System, single: total=4.00MiB, used=0.00B > Metadata, DUP: total=14.00GiB, used=10.58GiB > Metadata, single: total=8.00MiB, used=0.00B > GlobalReserve, single: total=512.00MiB, used=0.00B > > Kernel 3.19.8. > > Just to make sure I understand, do those messages in syslog mean that my > metadata got corrupted a bit, but because I have 2 copies, btrfs can fix > the bad copy by using the good one? > > Also, if my actual data got corrupted, am I correct that btrfs will > detect the checksum failure and give me a different error message of a > read error that cannot be corrected?
Yes, that's my reading of the situation. Note that the 3.19 kernel is the earliest I would expect this to be able to happen, as it's the first kernel that actually had the full set of parity RAID repair code in it. > I'll do a scrub later, for now I have to wait 20 hours for the raid rebuild > first. You'll probably find that the rebuild is equivalent to a scrub anyway. Hugo. -- Hugo Mills | If you're not part of the solution, you're part of hugo@... carfax.org.uk | the precipiate. http://carfax.org.uk/ | PGP: E2AB1DE4 |
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