[Bug 880645] Re: "btrfs device delete /dev/sdaX /" fails with error "ERROR: error removing the device '/dev/sdaX'"

[Thomas Mayer]

With Ubuntu 14.04, Kernel 3.16 (from HES), I could btrfs-balance a non-
raid /dev/sda2 btrfs fs with

cd /mnt
mkdir fulldisk
mount /dev/sda2 fulldisk
btrfs device add /dev/sdb fulldisk
btrfs balance start fulldisk
btrfs device delete /dev/sdb fulldisk

But with Ubuntu 14.04, Kernel 4.2.0-30-generic btrfs-delete gives me a
message

"error removing the device '/dev/sdb' - unable to go below two devices
on raid1"

It does not make sense to me why btrfs is reporting a raid 1 (mirroring)
instead of a raid 0 (for adding a device).

I consider this to be a regression (or at least a change in behaviour)
somewhere between kernel 3.16 and kernel 4.2. Note that I'm still using
the same btrfs-tools (3.12), so the change in behaviour should have
happened in the kernel.

-----------

I have:

btrfs filesystem show
Label: none  uuid: 16120d81-8cde-4e81-87cd-f55f65a4923b
        Total devices 2 FS bytes used 1.99TiB
        devid    1 size 2.73TiB used 1.81TiB path /dev/sda2
        devid    2 size 465.76GiB used 200.03GiB path /dev/sdb

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to btrfs-tools in Ubuntu.
https://bugs.launchpad.net/bugs/880645

Title:
  "btrfs device delete /dev/sdaX /" fails with error "ERROR: error
  removing the device '/dev/sdaX'"

Status in btrfs-tools package in Ubuntu:
  Confirmed

Bug description:
  What I did to cause this:

  Installed ubuntu using btrtfs root.
  Added a device with 'btrfs device add /dev/sda9 /'
  Balanced the file system with 'btrfs filesystem balance /'
  Tried to remove a device with 'btrfs device delete /dev/sda9 /'. Noticed that I got the error "ERROR: error removing the device '/dev/sda9'".

  (Unfortunately, I'm not sure how to get more information on the
  problem.)

  ProblemType: Bug
  DistroRelease: Ubuntu 11.10
  Package: btrfs-tools 0.19+20100601-3ubuntu3
  ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
  Uname: Linux 3.0.0-12-generic x86_64
  NonfreeKernelModules: nvidia wl
  ApportVersion: 1.23-0ubuntu3
  Architecture: amd64
  Date: Mon Oct 24 00:44:42 2011
  InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111010)
  ProcEnviron:
   LC_CTYPE=C
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/zsh
  SourcePackage: btrfs-tools
  UpgradeStatus: No upgrade log present (probably fresh install)

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/btrfs-tools/+bug/880645/+subscriptions