On 2016-09-12 08:54, Imran Geriskovan wrote:
On 9/11/16, Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote:
Something else that's screwy in that bug that I just realized, why is
it not defaulting to mixed-block groups on a 100MiB fallocated file? I
thought mixed-bg was the default below a certain size like 2GiB or
whatever?
With an ordinary partition on a single disk,
fs created with just "mkfs.btrfs /dev/sdxx":
- 128MB works fine.
- 127MB works but as if it is 64MB.
Can we say size should be in multiples of 64MB?
Why should it be in multiples? I think what you're describing is part
of the bug above that just needs to be fixed. Btrfs itself internally
uses bytes, so multiples of 64MiB is OK but I wouldn't use the word
"should" with it.
I'm not suggesting anything. I'm just describing the behaviour
we've seen. If it is (or will be) something different its all ok for me.
But, what is that "formal behaviour" at the low end?
That is the discussion..
Formally, with mixed-bg and otherwise default options, you should be
able to get to about 48-49% of the total size of the FS worth of data
stored. In practice, I see such filesystems start having issues at
about 45% of the total size. Note that this is not the percentages
reported by regular df (which should say about 90% full in this case), b
ut a comparison based on du -sh and the size of the partition.
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