[ceph-users] Is replacing OSD whose data is on HDD and DB is on SSD supported?

​Hi, I've been trying with v15.2 and v15.2.8, no luck. Wondering if this is actually supported or ever worked for anyone? Here is what I've done. 1) Create a cluster with 1 controller (mon and mgr) and 3 OSD nodes, each of which is with 1 SSD for DB and 8 HDDs for data. 2) OSD service spec. service_type: osd service_id: osd-spec placement: hosts: - ceph-osd-1 - ceph-osd-2 - ceph-osd-3 spec: block_db_size: 92341796864 data_devices: model: ST16000NM010G db_devices: model: KPM5XRUG960G 3) Add OSD hosts and apply OSD service spec. 8 OSDs (data on HDD and DB on SSD) are created on each host properly. 4) Run "orch osd rm 1 --replace --force". OSD is marked "destroyed" and reweight is set to 0 in "osd tree". "pg dump" shows no PG on that OSD. "orch ps" shows no daemon running for that OSD. 5) Run "orch device zap <host> <device>". VG and LV for HDD are removed. LV for DB stays. "orch device ls" shows HDD device is available. 6) Cephadm finds OSD claims and applies OSD spec on the host. Here is the message. ============================ cephadm [INF] Found osd claims -> {'ceph-osd-1': ['1']} cephadm [INF] Found osd claims for drivegroup osd-spec -> {'ceph-osd-1': ['1']} cephadm [INF] Applying osd-spec on host ceph-osd-1... cephadm [INF] Applying osd-spec on host ceph-osd-2... cephadm [INF] Applying osd-spec on host ceph-osd-3... cephadm [INF] ceph-osd-1: lvm batch --no-auto /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg /dev/sdh /dev/sdi /dev/sdj --db-devices /dev/sdb --block-db-size 92341796864 --osd-ids 1 --yes --no-systemd code: 0 out: [''] err: ['/bin/docker:stderr --> passed data devices: 8 physical, 0 LVM', '/bin/docker:stderr --> relative data size: 1.0', '/bin/docker:stderr --> passed block_db devices: 1 physical, 0 LVM', '/bin/docker:stderr --> 1 fast devices were passed, but none are available'] ============================ Q1. Is DB LV on SSD supposed to be deleted or not, when replacing an OSD whose data is on HDD and DB is on SSD? Q2. If yes from Q1, is a new DB LV supposed to be created on SSD as long as there is sufficient free space, when building the new OSD? Q3. If no from Q1, since it's replacing, is the old DB LV going to be reused for the new OSD? Again, is this actually supposed to work? Am I missing anything or just trying on some unsupported feature? Thanks! Tony