[ceph-users] Understanding op_r, op_w vs op_rw

Hi, I'd like to gain a better understanding about what operations emit which of these performance counters, in particular when is 'op_rw' incremented instead of 'op_r' + 'op_w'? I've done a little bit of investigation (v12.2.13) , running various workoads and operations against an RBD volume (in a cluster with no other client activity): - Most RBD 'operations'  (create, rm, features disable/enable, map, unmap) emit 'op_rw' and often 'op_w' too - Program reads and writes against a mounted RBD volume *only* emit 'op_r' and 'op_w' (never 'op_rw'), regardless of whether they are 'read + modify' of existing file data (or whether the writes are buffered, direct or sync) Is that correct? Or have I missed a program driven workload that will produce 'op_rw'? [1] In our production clusters I'm seeing similar numbers of 'op_w' and 'op_rw' (for a given OSD), which would suggest a lot of RBD operations if it is only them that cause 'op_rw' counters to be emitted. Cheers Mark [1] Tested using fio and pgbench (database benchmark). I mounted the volume using the kernel driver (I'll do some more experimentation using librbd)