Re: device delete, error removing device

[dima <dolenin@parallels.com>]

On 10/22/2012 01:32 PM, Chris Murphy wrote:
> Summary: 3 drive raid0 btrfs volume, in a VM. There is no data at risk at all. Purely a test. The volume is pretty much full. I added a larger drive /dev/sde to the existing btrfs volume; then tried to remove one of the smaller drives. I'm getting an error removing the device. It seems this should be possible, e.g. move extents on a failing device to a replacement prior to failure.
>
> This is stock Fedora 18 beta kernel, 3.6.1-1.fc18.x86_64 #1 SMP Mon Oct 8 17:19:09 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
>
>
> [root@f18v ~]# btrfs device add /dev/sde /mnt
> [root@f18v ~]# btrfs fi show
> failed to read /dev/sr0
> Label: none  uuid: 6e96a96e-3357-4f23-b064-0f0713366d45
> 	Total devices 4 FS bytes used 7.52GB
> 	devid    4 size 12.00GB used 0.00 path /dev/sde
> 	devid    3 size 3.00GB used 3.00GB path /dev/sdd
> 	devid    2 size 3.00GB used 2.55GB path /dev/sdc
> 	devid    1 size 3.00GB used 3.00GB path /dev/sdb
> 	
> [root@f18v ~]# btrfs fi df /mnt
> Data, RAID0: total=7.61GB, used=7.51GB
> System, RAID1: total=8.00MB, used=4.00KB
> Metadata, RAID1: total=460.75MB, used=10.91MB
> 	
> [root@f18v ~]# btrfs device delete /dev/sdb /mnt
> ERROR: error removing the device '/dev/sdb' - No space left on device
> 	
> [  570.379652] btrfs: relocating block group 29360128 flags 20
> [  571.739126] btrfs: found 2717 extents
> [  571.761061] btrfs: relocating block group 12582912 flags 1
> [  571.787233] btrfs: relocating block group 4194304 flags 4
> [  571.806878] btrfs: relocating block group 0 flags 2
>
> Some time later (hours), I unmounted, remounted, and see this:
>
> [root@f18v ~]# btrfs fi show
> failed to read /dev/sr0
> Label: none  uuid: 6e96a96e-3357-4f23-b064-0f0713366d45
> 	Total devices 4 FS bytes used 7.52GB
> 	devid    4 size 12.00GB used 460.75MB path /dev/sde
> 	devid    3 size 3.00GB used 2.55GB path /dev/sdd
> 	devid    2 size 3.00GB used 3.00GB path /dev/sdc
> 	devid    1 size 3.00GB used 2.53GB path /dev/sdb
>
> Subsequent attempts cause the same failure, but no new entries in dmesg.
>
> If I try with a different device, there is activity, but after a few seconds, another failure, similar errors in dmesg:
>
> [root@f18v ~]# btrfs device delete /dev/sdc /mnt
> ERROR: error removing the device '/dev/sdc' - No space left on device
>
>
> [ 2478.017828] btrfs: relocating block group 8955363328 flags 20
> [ 2478.059607] btrfs: relocating block group 8686927872 flags 20
> [ 2479.405142] btrfs: found 2735 extents
> [ 2479.436190] btrfs: relocating block group 8663859200 flags 9
> [ 2479.458680] btrfs: relocating block group 8243118080 flags 9
> [ 2481.949991] btrfs: found 4 extents
> [ 2482.700146] btrfs: found 4 extents
> [ 2482.717422] btrfs: relocating block group 20971520 flags 18
> [ 2482.733835] btrfs: found 1 extents
>
> User error? Known bug?


Might be you need to balance first after adding a new disk
btrfs filesystem balance /mnt