Bluestore does not defer writes

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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.

Any tips?

Regards Dennis
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