On Fri, Apr 8, 2016 at 12:56 AM, Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote: > You could use the 'degraded' mount option in fstab, but then that > shows as a mount option and kernel messages, the same as if you're > really degraded. So you have no idea if you're really degraded or not > unless you check 'btrfs fi show' or 'btrfs fi us'. > > You really need to know if you've mounted degraded because there's no > automatic rebuilds either. There's actually a more pernicious problem that affects degraded raid1 writes (and probably raid10): Degraded writes are marked as single copy, not raid1. So even after the missing device is found and you remount normally, and either scrub or balance, data written while degraded is not raid1. You actually have a device with mixed profile chunks. Example: [root@f23s ~]# btrfs fi df /mnt/1 Data, RAID1: total=1.00GiB, used=458.06MiB Data, single: total=1.00GiB, used=824.00MiB System, RAID1: total=64.00MiB, used=16.00KiB System, single: total=32.00MiB, used=0.00B Metadata, RAID1: total=2.00GiB, used=576.00KiB Metadata, single: total=256.00MiB, used=912.00KiB GlobalReserve, single: total=16.00MiB, used=0.00B There are two files on this file system. A 458M file was copied while two devices were normally mounted, so that file is in a chunk with raid1 profile. While mounted degraded with a device missing, a 824M file was copied, and that caused the creation of a new chunk with single profile to be created. Even if I do a normal scrub or balance, that data *and* its associated metadata, isn't made raid1. Upstream knows about this. It doesn't happen to raid56 profiles. It will get fixed, I just don't know when. The work around is: btrfs balance start -dconvert=raid1,soft -mconvert=raid1,soft /mnt/1 That converts non-raid1 chunks into raid1 chunks, skipping the ones that are already raid1. The result is df will only show raid1 chunks now, which is what you want. Anyway, yet another reason to do not setup silent degraded Btrfs mounts. -- Chris Murphy -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: http://lists.fedoraproject.org/admin/lists/users@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
