Re: Again, no space left on device while rebalancing and recipe doesnt work

[Hugo Mills <hugo@carfax.org.uk>]

[-- Attachment #1: Type: text/plain, Size: 2199 bytes --]

On Sun, Feb 28, 2016 at 01:08:29AM +0100, Marc Haber wrote:
> On Sun, Feb 28, 2016 at 12:15:21AM +0100, Martin Steigerwald wrote:
> > On Samstag, 27. Februar 2016 22:14:50 CET Marc Haber wrote:
> > > I have again the issue of no space left on device while rebalancing
> > > (with btrfs-tools 4.4.1 on kernel 4.4.2 on Debian unstable):
> > > 
> > > mh@fan:~$ sudo btrfs balance start /mnt/fanbtr
> > > ERROR: error during balancing '/mnt/fanbtr': No space left on device
> > > mh@fan:~$ sudo btrfs fi show /mnt/fanbtr
> > > mh@fan:~$ sudo btrfs fi show -m
> > > Label: 'fanbtr'  uuid: 4198d1bc-e3ce-40df-a7ee-44a2d120bff3
> > >         Total devices 1 FS bytes used 116.49GiB
> > >         devid    1 size 417.19GiB used 177.06GiB path /dev/mapper/fanbtr
> > 
> > Hmmm, thats still a ton of space to allocate chunks from.
> > 
> > > mh@fan:~$ sudo btrfs fi df /mnt/fanbtr
> > > Data, single: total=113.00GiB, used=112.77GiB
> > > System, DUP: total=32.00MiB, used=48.00KiB
> > > Metadata, DUP: total=32.00GiB, used=3.72GiB
> > > GlobalReserve, single: total=512.00MiB, used=0.00B
> > > mh@fan:~$
> > > 
> > > The filesystem was recently resized from 300 GB to 420 GB.
> > > 
> > > Why does btrfs fi show /mnt/fanbtr not give any output? Wy does btrfs
> > > fi df /mnt/fanbtr say that my data space is only 113 GiB large?
> > 
> > Cause it is.
> > 
> > The "used" in "devid 1" line is btrfs fi sh is "data + 2x system + 2x metadata 
> > = 113 GiB + 2 * 32 GiB + 2 * 32 MiB, i.e. what amount of the size of the 
> > device is allocated for chunks.
> > 
> > The value one line above is what is allocated inside the chunks.
> > 
> > I.e. the line in "devid 1" is "total" of btrfs fi df summed up, and the line 
> > above is "used" in btrfs fi df summed up. And… with more devices you have more 
> > fun.
> 
> Why wouldn't btrfs allocate more data chunks from the ample free space?

   It's a bug. It's been around for years (literally), but nobody's
tracked it down and fixed it yet.

   Hugo.

-- 
Hugo Mills             | We believe in free will because we have no choice.
hugo@... carfax.org.uk |
http://carfax.org.uk/  |
PGP: E2AB1DE4          |

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 836 bytes --]