Data, RAID1: total=417.12GiB, used=131.33GiB

You have 417(total)-131(used) blocks wo are only partial filled.
You should balance your file-system.

At first you need some free space. You could remove some files / old
snapshots etc. or you add a empty USB-Stick with min. 4 GB to your
BTRFS-Pool (after balancing complete you can remove the stick from the

But at first you should try to free emty data and meta data blocks:

btrfs balance start -musage=0 /mnt
btrfs balance start -dusage=0 /mnt

Then you an run a full balance or a partial balance:

#a partial balance with reorganize data blocks less then 50% filled
btrfs balance start -dusage=50 /mnt

#or a full balance
btrfs balance start /mnt

Because of a possible bug you should disable all snapshot scripts
(like cron-jobs) during the balance.

If this solve the "No space left" issues you must remove old snapshots.

2016-09-20 8:58 GMT+02:00 Hugo Mills <>:
> On Tue, Sep 20, 2016 at 03:47:14PM +0900, Tomasz Chmielewski wrote:
>> How to understand the following "btrfs fi show" output?
> This gives a write-up (and worked example) of an answer to your question:
>    If you've got any follow-up questions after reading it, please do
> come back and we can try to improve the FAQ entry. :)
>    Hugo.
>> # btrfs fi show /var/lib/lxd
>> Label: 'btrfs'  uuid: f5f30428-ec5b-4497-82de-6e20065e6f61
>>         Total devices 2 FS bytes used 136.18GiB
>>         devid    1 size 423.13GiB used 423.13GiB path /dev/sda3
>>         devid    2 size 423.13GiB used 423.13GiB path /dev/sdb3
>> Why is it "size 423.13GiB used 423.13GiB"? Is it full?
>> I had "No space left" on this filesystem just yesterday (running
>> kernel 4.7.4). This is btrfs RAID-1 on SSD disks. This filesystem is
>> used for 20-30 LXD containers with different roles (mongo, mysql,
>> postgres databases, webservers etc.), around 150 read-only
>> snapshots, btrfs compression is disabled.
>> Both "btrfs fi df" and "df -h" show plenty of space:
>> # btrfs fi df /var/lib/lxd
>> Data, RAID1: total=417.12GiB, used=131.33GiB
>> System, RAID1: total=8.00MiB, used=80.00KiB
>> Metadata, RAID1: total=6.00GiB, used=4.86GiB
>> GlobalReserve, single: total=512.00MiB, used=0.00B
>> # df -h
>> Filesystem      Size  Used Avail Use% Mounted on
>> /dev/sda3       424G  137G  286G  33% /var/lib/lxd
>> Tomasz Chmielewski
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> Hugo Mills             | I can resist everything except temptation.
> hugo@... |
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