Hi there. >From my limited understanding, btrfs will write metadata in raid1 by default. So, this could be where your 2TB has gone.
I am assuming you used raid0 for the three new disks? Also, hard-stopping a btrfs is a no-no... Kind regards, -Evert- On Mon, Mar 28, 2011 at 6:17 AM, Stephane Chazelas <stephane.chaze...@gmail.com> wrote: > 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 > -- -Evert- -- 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
