Hallo, Ilya,

Du meintest am 21.03.12:

quoted

When I run

        btrfs filesystem label

or

        btrfs scrub status /dev/sdxn

then I get a lot of error messages with (p.e.)

  failed to read /dev/hda6: No such device or address
  failed to read /dev/sdm7: No such device or address
  failed to read /dev/sr3: No such device or address

I think this has been fixed in recent btrfs-progs, commit 32eff711.

It is fixed in some (or many) places, it is not fixed everywhere. I had  
used kernel 3.2.9

Viele Gruesse!
Helmut