Re: No space left on device (again)

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

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On Tue, Feb 25, 2014 at 10:27:58PM +0200, Marcus Sundman wrote:
> On 25.02.2014 22:19, Hugo Mills wrote:
> >On Tue, Feb 25, 2014 at 01:05:51PM -0500, Jim Salter wrote:
> >>370GB of 410GB used isn't really "fine", it's over 90% usage.
> >>
> >>That said, I'd be interested to know why btrfs fi show /dev/sda3
> >>shows 412.54G used, but btrfs fi df /home shows 379G used...
> >    This is an FAQ...
> >
> >    btrfs fi show tells you how much is allocated out of the available
> >pool on each disk. btrfs fi df then shows how much of that allocated
> >space (in each category) is used.
> 
> What is the difference between the "used 371.11GB" and the "used
> 412.54GB" displayed by "btrfs fi show"?

   The first and smaller value is (in this case) the sum of all the
"used" values in the output of btrfs fi df. The second is the total
amount of raw disk space that has been allocated. (Yes, this is a bit
of a mess -- there's been discussions recently about improving the
output).

> >    The problem here is also in the FAQ: the metadata is close to full
> >-- typically something like 500-750 MiB of headroom is needed in
> >metadata. The FS can't allocate more metadata because it's allocated
> >everything already (total=used in btrfs fi show), so the solution is
> >to do a filtered balance:
> >
> >btrfs balance start -dusage=5 /mountpoint
> 
> Of course that was the first thing I tried, and it didn't help *at* *all*:
> 
> ># btrfs filesystem balance start -dusage=5 /home
> >Done, had to relocate 0 out of 415 chunks
> >#
> 
> ... and it really didn't free anything.

   OK, so crank up the number to 10 and try again. If that still moves
nothing, then increase again until it frees up something. With an FS
at 90% full or so, particularly if it's seen heavy use, the chances
are reasonable that all of the chunks are over 5% full, so putting the
value up will eventually get to the point of moving at least one
chunk, which should be all that's needed at this point.

   Hugo.

> >>On 02/25/2014 11:49 AM, Marcus Sundman wrote:
> >>>Hi
> >>>
> >>>I get "No space left on device" and it is unclear why:
> >>>
> >>>># df -h|grep sda3
> >>>>/dev/sda3       413G  368G   45G  90% /home
> >>>># btrfs filesystem show /dev/sda3
> >>>>Label: 'home'  uuid: 46279061-51f4-40c2-afd0-61d6faab7f60
> >>>>    Total devices 1 FS bytes used 371.11GB
> >>>>    devid    1 size 412.54GB used 412.54GB path /dev/sda3
> >>>>
> >>>>Btrfs v0.20-rc1
> >>>># btrfs filesystem df /home
> >>>>Data: total=410.52GB, used=369.61GB
> >>>>System: total=4.00MB, used=64.00KB
> >>>>Metadata: total=2.01GB, used=1.50GB
> >>>>#
> >>>So, 'data' and 'metadata' seem to be fine(?), but 'system' is a
> >>>bit low. Is that it? If so, can I do something about it? Or should
> >>>I look somewhere else?
> >>>
> >>>I really wish I could get a warning before running out of disk
> >>>space, instead of everything breaking suddenly when there seems to
> >>>be lots and lots of space left.
> >>>
> >>>- Marcus
> >>>
> 

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
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    --- Jazz is the sort of music where no-one plays anything the ---    
                             same way once.                              

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