Hi Patrik, [root@Xen ~]# uname -r 4.4.5-1-ARCH
[root@Xen ~]# pacman -Q btrfs-progs btrfs-progs 4.4.1-1 Your information below was very helpful and I was able to recreate the Raid array. However my initial question still stands - What if the drives dies completely? I work in a Data center and we see this quite a lot where a drive is beyond dead - The OS will literally not detect it. At this point would the Raid10 array be beyond repair? As you need the drive present in order to mount the array in degraded mode. -- Stephen Williams steph...@veryfast.biz On Fri, Mar 25, 2016, at 02:57 PM, Patrik Lundquist wrote: > On Debian Stretch with Linux 4.4.6, btrfs-progs 4.4 in VirtualBox > 5.0.16 with 4*2GB VDIs: > > # mkfs.btrfs -m raid10 -d raid10 /dev/sdb /dev/sdc /dev/sdd /dev/sdbe > > # mount /dev/sdb /mnt > # touch /mnt/test > # umount /mnt > > Everything fine so far. > > # wipefs -a /dev/sde > > *reboot* > > # mount /dev/sdb /mnt > mount: wrong fs type, bad option, bad superblock on /dev/sdb, > missing codepage or helper program, or other error > > In some cases useful info is found in syslog - try > dmesg | tail or so. > > # dmesg | tail > [ 85.979655] BTRFS info (device sdb): disk space caching is enabled > [ 85.979660] BTRFS: has skinny extents > [ 85.982377] BTRFS: failed to read the system array on sdb > [ 85.996793] BTRFS: open_ctree failed > > Not very informative! An information regression? > > # mount -o degraded /dev/sdb /mnt > > # dmesg | tail > [ 919.899071] BTRFS info (device sdb): allowing degraded mounts > [ 919.899075] BTRFS info (device sdb): disk space caching is enabled > [ 919.899077] BTRFS: has skinny extents > [ 919.903216] BTRFS warning (device sdb): devid 4 uuid > 8549a275-f663-4741-b410-79b49a1d465f is missing > > # touch /mnt/test2 > # ls -l /mnt/ > total 0 > -rw-r--r-- 1 root root 0 mar 25 15:17 test > -rw-r--r-- 1 root root 0 mar 25 15:42 test2 > > # btrfs device remove missing /mnt > ERROR: error removing device 'missing': unable to go below four > devices on raid10 > > As expected. > > # btrfs replace start -B missing /dev/sde /mnt > ERROR: source device must be a block device or a devid > > Would have been nice if missing worked here too. Maybe it does in > btrfs-progs 4.5? > > # btrfs replace start -B 4 /dev/sde /mnt > > # dmesg | tail > [ 1618.170619] BTRFS info (device sdb): dev_replace from <missing > disk> (devid 4) to /dev/sde started > [ 1618.184979] BTRFS info (device sdb): dev_replace from <missing > disk> (devid 4) to /dev/sde finished > > Repaired! > > # umount /mnt > # mount /dev/sdb /mnt > # dmesg | tail > [ 1729.917661] BTRFS info (device sde): disk space caching is enabled > [ 1729.917665] BTRFS: has skinny extents > > All in all it works just fine with Linux 4.4.6. -- 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
