Hallo, Hugo,

Du meintest am 26.02.12:

quoted

My (planned) usual work (once a year or so):

        btrfs device add <biggerdevice> <path>
        btrfs filesystem balance <path>
        btrfs device delete <smallerdevice> <path>

   OK, the real problem you're seeing is that when btrfs removes a
device from the filesystem, that device is not modified in any way.
This means that the old superblock is left behind on it, containing
the FS label information. What you need to do is, immediately after
removing a device from the FS, zero the first part of the partition
with dd and /dev/zero.

Ok - I'll try again (not today ...).
If I remember correct in early times deleting only the first block of  
the partition didn't reach ...

My last try with "delete" let me believe that btrfs had deleted the  
"critical" informations; I had tested it with "blkid". But looking into  
the first sector of the partition may be more reliable.

quoted

I prefer LABELling the devices/partitions, and then I'd seen that
the option "-L" makes problems when I use it for more than 1 device/
partition.

[...]

   I say again, partitions are not labelled. *Filesystems* are
labelled. I think that with a GPT you can refer to the disk itself
and its partitions by a UUID each, but I'm not 100% certain.

My last try:

        mkfs.btrfs -d raid0 -m raid1 /dev/sdk1 /dev/sdl1 /dev/sdm1

        mkfs.btrfs -L SCSI /dev/sdk1

seemed to work.

        mount LABEL=SCSI /mnt/btr

worked as expected, the bundle of 3 partitions was mounted. And only "/ 
dev/sdk1" got this label, no other partition.

Viele Gruesse!
Helmut