Re: System/single + Metadata/single as leftover cruft of mkfs?

[Austin S Hemmelgarn]

On 2014-12-04 08:53, Shriramana Sharma wrote:

I observe that whenever I create a BtrFS instance using mkfs.btrfs,
there is always the leftover cruft of two System/Metadata-Single
allocation profiles:

btrfs fi df /run/media/samjnaa/BRIHATII/
Data, single: total=460.01GiB, used=458.47GiB
System, DUP: total=8.00MiB, used=80.00KiB
System, single: total=4.00MiB, used=0.00B
Metadata, DUP: total=1.50GiB, used=736.86MiB
Metadata, single: total=8.00MiB, used=0.00B
GlobalReserve, single: total=256.00MiB, used=0.00B

Doing btrfs balance eventually removes these (but since I forgot to do
it *before* copying 400+ G of data to the drive it's still running)
but I don't understand why these have to be created in the first
place? (I just used SuSE Tumbleweed's default mkfs.btrfs without any
-m or -d options.)

SuSE may have an old version of btrfs-progs then (which wouldn't surprise me, it is an 'enterprise' distribution after all), because I haven't seen this on anything since 3.16.

The really interesting thing in this case is that the metadata chunk is 8M, when they are usually 256M. Also, for future reference, you can use the switch -mprofiles=single to just balance out those chunks.

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