You /really/ need to read up on the btrfs wiki.
The short answer is yes, btrfs does a LOT more metadata processing
due to the checksumming it does by default.
According to the wiki, checksumming has barely any influence, so I
guess the above advice is not really helpful?
https://btrfs.wiki.kernel.org/index.php/Mount_options
nodatasum
(...)
On most modern CPUs this option does not result in any
reasonable performance improvement.
Then there's the whole problem that you didn't provide nearly enough
information about your test to tell what it was actually comparing.
What sort of raid1, btrfs/md/dm/hardware/what, and if btrfs raid1, was
that for both data and metadata or just one of the two and what was
the other one if they weren't both raid1? And if you were testing
btrfs raid1, what did you do with the ext4 test to try to make it
comparable since ext4 doesn't have a native raid1 mode, or was it on
a single device?
ext4: using md RAID
btrfs:
Data, RAID1: total=1.73TB, used=1.36TB
System, RAID1: total=32.00MB, used=264.00KB
System: total=4.00MB, used=0.00
Metadata, RAID1: total=79.00GB, used=70.23GB
Quite high metadata usage here.
The filesystems on ext4 and btrfs are copies; there are >30 milion
inodes on ext4; most of the files have multiple hardlinks.
So paraphrasing my question: is there anything to improve "rm"
performance with btrfs?
"nodatacow" might help a bit, but then, it disabled the compression,
which is a major drawback.
--
Tomasz Chmielewski
http://wpkg.org
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