Re: How to delete this snapshot, and how to succeed with balancing?

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

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On Sat, Oct 31, 2015 at 11:45:15PM +0100, Henk Slager wrote:
> Hi Simon,
> 
> >>> linux-va3e:~ # btrfs balance start -dlimit=2 /
> >>> ERROR: error during balancing '/' - No space left on device
> >>> There may be more info in syslog - try dmesg | tail
> >>
> >>    And this is with a filesystem that's not fully allocated?
> >> (i.e. btrfs fi show indicates that used and total are different for
> >> each device). If that's the case, then you may have hit a known but
> >> unfixed bug to do with space allocation.
> >
> > linux-va3e:~ # btrfs fi show
> > Label: none  uuid: 656dc65f-240b-4137-a490-0175717dd7fa
> >         Total devices 1 FS bytes used 13.71GiB
> >         devid    1 size 20.00GiB used 16.88GiB path /dev/sda2
> >
> > btrfs-progs v4.0+20150429
> >
> > Is there a manual work-around?

   Not that we've found in the last year or so of poking at it, I'm
afraid.

> For 'No space left on device', a trick I once saw is to run:
> 
> btrfs balance start -dusage=0 -musage=0 /
> 
> Under certain circumstances (i don't remember which kernel, tools
> versions etc), this enables you to create files again on the
> filesystem.

   That's basically what Simon's been doing (although a little more
aggressively). It's not going to help here.

> Looking at the   btrfs fi df /  output, I don't see a real need for
> balancing, the numbers can be much different and then balance might be
> usefull.

   If you're hitting ENOSPC with unallocated space, then that's a
bug. In fact, it's a known bug that hasn't been fixed yet.

   Hugo.

-- 
Hugo Mills             | That's not rain, that's a lake with slots in it.
hugo@... carfax.org.uk |
http://carfax.org.uk/  |
PGP: E2AB1DE4          |

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