Re: 800 GByte free, but "no space left"

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

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On Mon, Dec 06, 2010 at 02:13:00PM +0100, Helmut Hullen wrote:
> Hallo, Hugo,
> 
> Du meintest am 06.12.10:
> 
> >>>> But after copying about 300 MByte (part of a 1.5-GByte *.mpg) I
> >>>> got "no space left on device". Looks like balancing has stolen
> >>>> about 300 GByte.
> >>
> >>>    This sounds exactly like a problem I've had. What output do you
> >>> get from "btrfs fi df /srv/MM"?
> >>
> >> I've just written a script for gathering the (perhaps) interesting
> >> data ...
> >>
> >> # btrfs filesystem show
> >> Label: 'MM2'  uuid: ad7c0668-316c-4a79-ba00-3b505b9d99b4
> >> 	Total devices 2 FS bytes used 2.37TB
> >> 	devid    2 size 1.35TB used 1.20TB path /dev/sdc3
> >> 	devid    1 size 1.81TB used 1.20TB path /dev/sdf2
> >>
> >> Btrfs Btrfs v0.19
> >>
> >> # btrfs filesystem df /srv/MM
> >> Data: total=2.39TB, used=2.37TB
> >> Metadata: total=5.25GB, used=3.51GB
> >> System: total=12.00MB, used=188.00KB
> 
> >    Can you try that again with either the latest 2.6.37-rc, or with
> > the btrfs-unstable kernel? There's a bug in earlier versions that
> > breaks the reporting of RAID types, which is what I wanted to see
> > here.
> 
> Do you mean
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable.git
> 
> as "btrfs-unstable kernel"?

   Yes. It's 2.6.36, plus the patches that Chris has sent to Linus for
inclusion into 2.6.37.

> Compiling 2.6.37-rc is no big problem, it only needs som time.
> 
> Just now I'm using
> 
> Kernel 2.6.35.8
> btrfs-git from 20101117
> 
> >> I've moved about 50 Gbyte away from "srv/MM" in the meantime, before
> >> running the script with this output.
> >>
> >> And I don't dare running "balance" again - maybe it reduces the
> >> available space again and again.
> 
> >    If you've hit the bug I think you have, then yes, it will.
> 
> Hmm - it can't get worse ...
> If the error is related to the kernel or to the btrfs version and I try  
> a newer one: can that lead to more free space?

   Not yet. I've taken the whole of December off work (using up my
leave allocation for last year), and my plan is to get myself to the
point where I can understand enough of the code to fix this particular
problem.

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
  PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
    --- "What are we going to do tonight?" "The same thing we do ---     
            every night, Pinky.  Try to take over the world!"            

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