[ceph-users] Bluestore performance tuning for hdd with nvme db+wal

Hi, We have recently added a new storage node to our Luminous (12.2.13) cluster. The prev nodes are all setup as Filestore: e.g 12 osds on hdd (Seagate Constellations) with one NVMe (Intel P4600) journal. With the new guy we decided to introduce Bluestore so it is configured as: (same HW) 12 osd with data on hdd and db + wal on one NVMe. We noticed there are periodic slow requests logged, and the implicated osds are the Bluestore ones 98% of the time! This suggests that we need to tweak our Bluestore settings in some way. Investigating I'm seeing: - A great deal of rocksdb debug info in the logs - perhaps we should tone that down? (debug_rocksdb 4/5 -> 1/5) - We look to have the default cache settings (bluestore_cache_size_hdd|ssd etc), we have memory to increase these - There are some buffered io settings (bluefs_buffered_io, bluestore_default_buffered_write), set to (default) false. Are these safe (or useful) to change? - We have default rocksdb options, should some of these be changed? (bluestore_rocksdb_options, in particular max_background_compactions=2 - should we have less, or more?) Also, anything else we should be looking at? regards Mark