On Samstag, 27. Februar 2016 22:14:50 CET Marc Haber wrote:
> Hi,
Hi Marc.
> I have again the issue of no space left on device while rebalancing
> (with btrfs-tools 4.4.1 on kernel 4.4.2 on Debian unstable):
>
> mh@fan:~$ sudo btrfs balance start /mnt/fanbtr
> ERROR: error during balancing '/mnt/fanbtr': No space left on device
> mh@fan:~$ sudo btrfs fi show /mnt/fanbtr
> mh@fan:~$ sudo btrfs fi show -m
> Label: 'fanbtr' uuid: 4198d1bc-e3ce-40df-a7ee-44a2d120bff3
> Total devices 1 FS bytes used 116.49GiB
> devid 1 size 417.19GiB used 177.06GiB path /dev/mapper/fanbtr
Hmmm, thats still a ton of space to allocate chunks from.
> mh@fan:~$ sudo btrfs fi df /mnt/fanbtr
> Data, single: total=113.00GiB, used=112.77GiB
> System, DUP: total=32.00MiB, used=48.00KiB
> Metadata, DUP: total=32.00GiB, used=3.72GiB
> GlobalReserve, single: total=512.00MiB, used=0.00B
> mh@fan:~$
>
> The filesystem was recently resized from 300 GB to 420 GB.
>
> Why does btrfs fi show /mnt/fanbtr not give any output? Wy does btrfs
> fi df /mnt/fanbtr say that my data space is only 113 GiB large?
Cause it is.
The "used" in "devid 1" line is btrfs fi sh is "data + 2x system + 2x metadata
= 113 GiB + 2 * 32 GiB + 2 * 32 MiB, i.e. what amount of the size of the
device is allocated for chunks.
The value one line above is what is allocated inside the chunks.
I.e. the line in "devid 1" is "total" of btrfs fi df summed up, and the line
above is "used" in btrfs fi df summed up. And… with more devices you have more
fun.
I suggest:
merkaba:~> btrfs fi usage -T /daten
Overall:
Device size: 235.00GiB
Device allocated: 227.04GiB
Device unallocated: 7.96GiB
Device missing: 0.00B
Used: 225.84GiB
Free (estimated): 8.48GiB (min: 8.48GiB)
Data ratio: 1.00
Metadata ratio: 1.00
Global reserve: 128.00MiB (used: 0.00B)
Data Metadata System
Id Path single single single Unallocated
-- --------- --------- --------- -------- -----------
1 /dev/dm-1 226.00GiB 1.01GiB 32.00MiB 7.96GiB
-- --------- --------- --------- -------- -----------
Total 226.00GiB 1.01GiB 32.00MiB 7.96GiB
Used 225.48GiB 371.83MiB 48.00KiB
as that is much clearer to read IMHO.
and
merkaba:~> btrfs device usage /daten
/dev/dm-1, ID: 1
Device size: 235.00GiB
Data,single: 226.00GiB
Metadata,single: 1.01GiB
System,single: 32.00MiB
Unallocated: 7.96GiB
(although thats include in the filesystem usage output)
Or for a BTRFS RAID 1:
merkaba:~> btrfs fi usage -T /home
Overall:
Device size: 340.00GiB
Device allocated: 340.00GiB
Device unallocated: 2.00MiB
Device missing: 0.00B
Used: 306.47GiB
Free (estimated): 14.58GiB (min: 14.58GiB)
Data ratio: 2.00
Metadata ratio: 2.00
Global reserve: 512.00MiB (used: 0.00B)
Data Metadata System
Id Path RAID1 RAID1 RAID1 Unallocated
-- --------- --------- -------- -------- -----------
1 /dev/dm-0 163.94GiB 6.03GiB 32.00MiB 1.00MiB
2 /dev/dm-3 163.94GiB 6.03GiB 32.00MiB 1.00MiB
-- --------- --------- -------- -------- -----------
Total 163.94GiB 6.03GiB 32.00MiB 2.00MiB
Used 149.36GiB 3.88GiB 48.00KiB
merkaba:~> btrfs device usage /home
/dev/dm-0, ID: 1
Device size: 170.00GiB
Data,RAID1: 163.94GiB
Metadata,RAID1: 6.03GiB
System,RAID1: 32.00MiB
Unallocated: 1.00MiB
/dev/dm-3, ID: 2
Device size: 170.00GiB
Data,RAID1: 163.94GiB
Metadata,RAID1: 6.03GiB
System,RAID1: 32.00MiB
Unallocated: 1.00MiB
(this is actually the situation asking for hung task trouble with kworker
threads seeking for free space inside chunks, as no new chunks can be
allocated, lets hope kernel 4.4 finally really has fixes for this)
> btrfs balance start -dusage=5 works up to -dusage=100:
>
> mh@fan:~$ sudo btrfs balance start -dusage=100 /mnt/fanbtr
> Done, had to relocate 111 out of 179 chunks
> mh@fan:~$ sudo btrfs balance start -dusage=100 /mnt/fanbtr
> Done, had to relocate 111 out of 179 chunks
> mh@fan:~$ sudo btrfs balance start -dusage=100 /mnt/fanbtr
> Done, had to relocate 110 out of 179 chunks
> mh@fan:~$ sudo btrfs balance start -dusage=100 /mnt/fanbtr
> Done, had to relocate 109 out of 179 chunks
> mh@fan:~$ sudo btrfs balance start /mnt/fanbtr
> ERROR: error during balancing '/mnt/fanbtr': No space left on device
> mh@fan:~$
>
> What is going on here? How do I get away from here?
Others may have better tips, but what can always work is:
Adding a new device temporarily, doing the balance and then removing it.
Before that I´d try to balance the metadata chunks, cause
> Metadata, DUP: total=32.00GiB, used=3.72GiB
32 GiB chunks allocated, only 3,72 GiB used.
Maybe that way you can gain more free space to have a full balance run.
Also note that it is not necessary to do a full balance in case everything
works okayish.
Thanks,
--
Martin
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