Help! - "btrfs device delete missing" running out of space

["Piotr Pawłow" <pp@siedziba.pl>]

Hello,

I replaced a failed 500G disk in btrfs raid1 with 2 smaller ones - 200 
and 250GB. I started "btrfs device delete missing" command, which is 
running since friday, and it still seems far from finished.

It seems to be doing something very strange: used space on the largest 
drive is going down, while smaller drives are filling up to the brim.

I'm afraid it will soon run out of space and I don't know what to do.

The current situation is:

Label: none  uuid: cff1e711-97fe-4c1c-b8a3-6184010b5027
	Total devices 4 FS bytes used 376.66GB
	devid    4 size 172.81GB used 167.00GB path /dev/dm-16
	devid    3 size 232.88GB used 227.00GB path /dev/dm-4
	devid    2 size 452.26GB used 327.01GB path /dev/dm-0
	*** Some devices missing

According to btrfs FAQ and http://carfax.org.uk/btrfs-usage, there should 
be around 404GB of usable space in this configuration. Assuming even 
distribution, used space on each device should be accordingly: 160, 216, 
and 405. The current situation is FAR from that.

I'd be grateful for tips what do to and how to get out of this situation.

Regards