On 2015-08-11 07:08, Juan Orti Alcaine wrote:
> Hello,
>
> I have added a new disk to my filesystem and I'm doing a balance right
> now, but I'm a bit worried that the disk usage does not get updated as
> it should. I remember from earlier versions that you could see the
> disk usage being balanced across all disks.
>
> These are the commands I've run:
> # btrfs device add /dev/sdb2 /mnt/btrfs_raid1
> # btrfs fi balance /mnt/btrfs_raid1
>
> I see the unallocated space of sdc2 and sdd2 increasing, but for sdb2
> (the new disk), it doesn't change. sdb2 doesn't even appear in the
> btrfs usage command for data, metadata and system.
>
> Is this normal? It's very strange the disk not showing up in the usage report.
How much slack space was allocated by BTRFS before running the balance 
(ie, how big a difference was there between the allocated and used 
space), and did the balance run to completion?  If you had a lot of 
mostly empty chunks and stopped the balance part way through, then this 
is what I would expect to happen (balance back-fills partial chunks 
before it starts allocating new ones).

If that is not the case however, then this is very much _not_ normal, 
and is almost certainly a bug, in which case you should make sure any 
important data on the filesystem is backed up before doing anything 
further with it (including unmounting it or rebooting the system).