2011-03-22 18:06:29 -0600, cwillu: > > I can mount it back, but not if I reload the btrfs module, in which case I > > get: > > > > [ 1961.328280] Btrfs loaded > > [ 1961.328695] device fsid df4e5454eb7b1c23-7a68fc421060b18b devid 1 > > transid 118 /dev/loop0 > > [ 1961.329007] btrfs: failed to read the system array on loop0 > > [ 1961.340084] btrfs: open_ctree failed > > Did you rescan all the loop devices (btrfs dev scan /dev/loop*) after > reloading the module, before trying to mount again?
Thanks. That probably was the issue, that and using too big files on too small volumes I'd guess. I've tried it in real life and it seemed to work to some extent. So here is how I transferred a 6TB btrfs on one 6TB raid5 device (on host src) over the network onto a btrfs on 3 3TB hard drives (on host dst): on src: lvm snapshot -L100G -n snap /dev/VG/vol nbd-server 12345 /dev/VG/snap (if you're not lucky enough to have used lvm there, you can use nbd-server's copy-on-write feature). on dst: nbd-client src 12345 /dev/nbd0 mount /dev/nbd0 /mnt btrfs device add /dev/sdb /dev/sdc /dev/sdd /mnt # in reality it was /dev/sda4 (a little under 3TB), /dev/sdb, # /dev/sdc btrfs device delete /dev/nbd0 /mnt That was relatively fast (about 18 hours) but failed with an error. Apparently, it managed to fill up the 3 3TB drives (as shown by btrfs fi show). Usage for /dev/nbd0 was at 16MB though (?!) I then did a "btrfs fi balance /mnt". I could see usage on the drives go down quickly. However, that was writing data onto /dev/nbd0 so was threatening to fill up my LVM snapshot. I then cancelled that by doing a hard reset on "dst" (couldn't find any other way). And then: Upon reboot, I mounted /dev/sdb instead of /dev/nbd0 in case that made a difference and then ran the btrfs device delete /dev/nbd0 /mnt again, which this time went through. I then did a btrfs fi balance again and let it run through. However here is what I get: $ df -h /mnt Filesystem Size Used Avail Use% Mounted on /dev/sdb 8.2T 3.5T 3.2T 53% /mnt Only 3.2T left. How would I reclaim the missing space? $ sudo btrfs fi show Label: none uuid: ... Total devices 3 FS bytes used 3.43TB devid 4 size 2.73TB used 1.17TB path /dev/sdc devid 3 size 2.73TB used 1.17TB path /dev/sdb devid 2 size 2.70TB used 1.14TB path /dev/sda4 $ sudo btrfs fi df /mnt Data, RAID0: total=3.41TB, used=3.41TB System, RAID1: total=16.00MB, used=232.00KB Metadata, RAID1: total=35.25GB, used=20.55GB So that kind of worked but that is of little use to me as 2TB kind of disappeared under my feet in the process. Any idea, anyone? Thanks Stephane -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html