I'm struggling with a btrfs RAID0 filesystem.

It's expanded on 4 disks but i need to remove one of those disks.

This is the current status of the filesystem:

[root@osgiliath detlev]# btrfs fi show /mnt/Data/
Label: 'Data'  uuid: 4c15fe81-ca58-4ac5-adf7-bdde245496f0
        Total devices 4 FS bytes used 1.26TiB
        devid    1 size 2.68TiB used 612.55GiB path /dev/sdc2
        devid    2 size 74.53GiB used 74.52GiB path /dev/sda1
        devid    3 size 931.51GiB used 606.55GiB path /dev/sdc1
        devid    4 size 232.89GiB used 7.52GiB path /dev/sdb

and df:

[root@osgiliath detlev]# btrfs fi df /mnt/Data/
Data, RAID0: total=1.26TiB, used=1.26TiB
System, RAID1: total=32.00MiB, used=112.00KiB
Metadata, RAID1: total=3.00GiB, used=1.66GiB
GlobalReserve, single: total=512.00MiB, used=143.50MiB

I tried deleting /dev/sdc1 but it failed with No space left on device. I tried rebalancing (only metadata first then data also). It balanced some data but now, if I try to delete /dev/sdc1, it moves some (4G) data out of sdc1 to sdb then stops with "No space left on device". If I rebalance, it moves data back from sdb to sdc1.

I tried removing sdb too but it just says No space left on device.

I am not sure how I can remove that /dev/sdc1 (I know, there are 2 partitions on the same disk, this is due to a broken disk connector, i had to move it temporarily, this is why I want it removed)

Any idea ?

  • 1
    Which kernel version? Especially if you're on something a fair bit older, can you try it with the latest kernel? btrfs changes fairly fast. – derobert Jan 9 '16 at 11:22
  • It's a kernel 4.1.15 Is it too old ? – Detlev Casanova Jan 9 '16 at 21:06

You could try resizing devid 4 (sdb) to be 0 bytes: btrfs filesystem resize 4:0 /mnt/Data/.

If that fails it might be because there is a subvolume on /dev/sdb, you can check with: btrfs subvolume list /mnt/Data/

If there is a subvolume I suspect you will have to delete it, after moving important data out of it, before you can remove the device. It might take a btrfs filesystem sync /mnt/Data/ before the subvolume is completely removed.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.