On 31/08/2020 11:00, Dennis Benndorf wrote:
Hi,
today I recognized bad performance in our cluster. Running "watch ceph
osd perf |sort -hk 2 -r" I found that all bluestore OSDs are slow on
commit and that the commit timings are equal to their apply timings:
For example
Every 2.0s: ceph osd perf |sort -hk 2
-r
440 82 82
430 58 58
435 56 56
449 53 53
442 40 40
441 30 30
439 27 27
99 0 1
98 0 0
97 0 2
96 0 6
95 0 2
94 0 6
93 0 13
The once with zero commit timings are filestore and the others are
bluestore osds.
I did not see this after installing the new bluestore osds (maybe this
occured later).
Both types of osds have nvmes as journal/db. Servers have equal
cpus/ram etc.
The only tuning regarding bluestore is:
bluestore_block_db_size = 69793218560
bluestore_prefer_deferred_size_hdd = 524288
In order to make a filestore like behavior, but that does not seem to
work.
As far as I know is that with BlueStore apply and commit latencies are
equal.
Where did you get the idea that you could influence this with these
settings?
Wido
Any tips?
Regards Dennis
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