On Fri, Aug 12, 2016 at 11:36 AM, Ronan Arraes Jardim Chagas
[off-list ref] wrote:

Hi guys,

I'm facing a daily problem with BTRFS. Almost everyday, I get the
message "No space left on device". Sometimes I can recover by balancing
the system but sometimes even balancing does not work due to the lack
of space. In this case, only a hard reset works if I can't delete some
files. The problem is that I have a huge unallocated space as you can
see here:

# btrfs fi usage /
Overall:
    Device size:                   1.26TiB
    Device allocated:            119.07GiB
    Device unallocated:            1.14TiB

Tons of unallocated space. What kernel messages do you get for the
enospc? It sounds like this will be one of the mystery -28 error file
systems. So far as I recall the only work around is recreating the
file system. There are two additional things you can try: mount with
enospc_debug mount option and see if you can gather more information
about the problem. Or try a 4.8rc1 kernel which as a large number of
enospc changes.


-- 
Chris Murphy