On 4/5/20 12:57 PM, Graham Cobb wrote:
On 05/04/2020 09:26, Goffredo Baroncelli wrote:
[...]
Test description real (mmm:ss) Delta %
-------------------- ------------- -------
btrfs hdd w/sync 142:38 +533%
btrfs ssd+hdd w/sync 81:04 +260%
ext4 hdd w/sync 52:39 +134%
btrfs bcache w/sync 35:59 +60%
btrfs ssd w/sync 22:31 reference
ext4 ssd w/syn 12:19 -45%
Interesting data but it seems to be missing the case of btrfs ssd+hdd
w/sync without your patch in order to tell what difference your patch
made. Or am I confused?
Currently BTRFS allocates the chunk on the basis of the free space.
For my tests I have a smaller ssd (20GB) and a bigger hdd (230GB).
This means that the latter has higher priority for the allocation,
until the free space became equal.
The rationale behind my patch is the following:
- is quite simple (even tough in 3 iteration I put two errors :-) )
- BTRFS has already two kind of information to store: data and metadata.
The former is (a lot ) bigger, than the latter. Having two kind of storage,
one faster (and expensive) than the other, it is natural to put the metadata
in the faster one, and the data in the slower one.
BR
G.Baroncelli
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