On 2016/06/21 8:30, Marc Grondin wrote:

Hi everyone,


I have a btrfs filesystem ontop of a 4x1tb mdraid raid5 array and I've
been getting confusing output on metadata usage. Seems that even tho
both data and metadata are in single profile metadata is reporting
double the space(as if it was in dupe profile)



root@thebeach /h/marcg> uname -a
Linux thebeach 4.6.2-gentoo-GMAN #1 SMP Sat Jun 11 22:32:27 ADT 2016
x86_64 Intel(R) Core(TM) i5-2320 CPU @ 3.00GHz GenuineIntel GNU/Linux
root@thebeach /h/marcg> btrfs --version
btrfs-progs v4.5.3
root@thebeach /h/marcg> btrfs fi us /media/Storage2
Overall:
Device size: 2.73TiB
Device allocated: 1.71TiB
Device unallocated: 1.02TiB
Device missing: 0.00B
Used: 1.38TiB
Free (estimated): 1.34TiB (min: 1.34TiB)
Data ratio: 1.00
Metadata ratio: 1.00
Global reserve: 512.00MiB (used: 0.00B)


Data,single: Size:1.71TiB, Used:1.38TiB
/dev/mapper/storage2 1.71TiB


Metadata,single: Size:3.00GiB, Used:1.53GiB
/dev/mapper/storage2 3.00GiB


System,single: Size:32.00MiB, Used:208.00KiB
/dev/mapper/storage2 32.00MiB


Unallocated:
/dev/mapper/storage2 1.02TiB
root@thebeach /h/marcg> btrfs fi df /media/Storage2
Data, single: total=1.71TiB, used=1.38TiB
System, single: total=32.00MiB, used=208.00KiB
Metadata, single: total=3.00GiB, used=1.53GiB
GlobalReserve, single: total=512.00MiB, used=0.00B
root@thebeach /h/marcg>


I'm not sure if this is known and if it's btrfs-progs related or if it
is actually allocating that space.

Could you tell me the location where you think
metadata is reporting double the space?

from fi us:

Metadata,single: Size:3.00GiB, Used:1.53GiB
/dev/mapper/storage2 3.00GiB

from fi df:

Metadata,single: Size:3.00GiB, Used:1.53GiB
/dev/mapper/storage2 3.00GiB

As far as I can see, Btrfs just allocates 3.00 GiB
from /dev/mapper/storage2, Metadata,single size is
the same as it (not double), and 1.53 GiB is used.


The following is in my case where data is single
and meta is dup.

from fi us:
Metadata,DUP: Size:384.00MiB, Used:221.36MiB
   /dev/vda3     768.00MiB

from fi df:
Metadata, DUP: total=384.00MiB, used=221.36MiB

Here Btrfs allocates 768.0MiB from /dev/vda3 and it's
twice as large as the size of Metadata,DUP(384.00MiB).
I guess it means that "metadata is reporting double the space"
as you said and your case it not the case.

CMIIW.

Thanks,
Satoru

Thank you for reading.


Marc

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