Btrfs out of space - but plenty of space is available

[Konstantin Svist]

Looks like I'm having a problem with my btrfs partition, it thinks it's out
of space.
Thing is, the drive is 500G and usage according to df and btrfs df is ~250G
I removed a couple of snapshots as a workaround but hit the problem again
pretty quickly..
I also ran fstrim & btrfs check --clear-space-cache (both v1 and v2) and
still no luck.

Is there some limitation on number of files? I'm not doing anything crazy
there, just haven't checked yet

[Richard Shaw]

On Thu, Jun 11, 2020 at 6:38 PM Konstantin Svist <fry.kun(a)gmail.com&gt; wrote:

>  Looks like I'm having a problem with my btrfs partition, it
> thinks it's
>  out of space.
>  Thing is, the drive is 500G and usage according to df and btrfs df is ~250G
>  I removed a couple of snapshots as a workaround but hit the problem again
>  pretty quickly..
>  I also ran fstrim & btrfs check --clear-space-cache (both v1 and v2) and
>  still no luck.
>
>  Is there some limitation on number of files? I'm not doing anything crazy
>  there, just haven't checked yet
>  
This may be over simplistic, but I know btrfs needs free space because it's
a COW (Copy On Write) file system, but 250GB seems excessive.

Thanks,
Richard

[Neal Becker]

This happened to me before.  It's something similar to running out of
inodes.  Just do some googling and you should find the solution
(unfortunately I don't recall it).

On Thu, Jun 11, 2020 at 7:38 PM Konstantin Svist <fry.kun(a)gmail.com&gt; wrote:

>  Looks like I'm having a problem with my btrfs partition, it
> thinks it's
>  out of space.
>  Thing is, the drive is 500G and usage according to df and btrfs df is ~250G
>  I removed a couple of snapshots as a workaround but hit the problem again
>  pretty quickly..
>  I also ran fstrim & btrfs check --clear-space-cache (both v1 and v2) and
>  still no luck.
>
>  Is there some limitation on number of files? I'm not doing anything crazy
>  there, just haven't checked yet
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-- 
*Those who don't understand recursion are doomed to repeat it*

[Konstantin Svist]

After I wrote the question here, I realized what that I didn't google
for the condition well enough
Long story short, turns out sometimes btrfs reserves the space but
doesn't use it -- in this case, a good 40+% of the drive :(
Anyway, after a "btrfs balance" I think it's actually resolved.

# btrfs fi us /
Overall:
    Device size:         476.94GiB
    Device allocated:         279.98GiB

(before the rebalance, "allocated" was also ~476GiB)

~cheers


On 6/11/20 16:38, Konstantin Svist wrote:
>  Looks like I'm having a problem with my btrfs partition, it
> thinks
>  it's out of space.
>  Thing is, the drive is 500G and usage according to df and btrfs df is
>  ~250G
>  I removed a couple of snapshots as a workaround but hit the problem
>  again pretty quickly..
>  I also ran fstrim & btrfs check --clear-space-cache (both v1 and v2)
>  and still no luck.
>
>  Is there some limitation on number of files? I'm not doing anything
>  crazy there, just haven't checked yet