Hi, For testing purpose we need to deploy : - 1 pool of 6 SSD OSD - 1 pool of 6 HDD OSD - 1 pool of 6 HDD OSD with 2 SSD for DB+WAL I tried to orch apply this yaml but it doesn't work as expected Osd part of the yaml -> service_type: osd service_id: osd_spec placement: hosts: - host1 - host2 - host3 - host4 - host5 - host6 data_devices: paths: - /dev/sda - /dev/sdc spec: data_devices: all: true filter_logic: AND objectstore: bluestore --- service_type: osd service_id: osd_spec_wall placement: hosts: - host1 - host2 - host3 - host4 - host5 - host6 spec: data_devices: paths: - /dev/sdf db_devices: paths: - /dev/sde limit: 2 db_slots: 3 Only 1 db on /dev/sde from host1 has been created and this OSD showed up as half full at his creation: ceph osd df | grep 25 25 hdd 0.63669 1.00000 652 GiB 373 GiB 1.5 MiB 1 KiB 38 MiB 279 GiB 57.15 35.93 0 up ceph-volume lvm list ====== osd.25 ====== [block] /dev/ceph-23d9297a-d0e1-47be-8650-5c8ccae4fe0e/osd-block-2f009760-fc2b-46d5-984d-e8200dfd9d9d block device /dev/ceph-23d9297a-d0e1-47be-8650-5c8ccae4fe0e/osd-block-2f009760-fc2b-46d5-984d-e8200dfd9d9d block uuid vqJGf8-V5g0-S1cA-BAcN-Qm9D-9VTx-xsc8wk cephx lockbox secret cluster fsid id cluster name ceph crush device class db device /dev/ceph-9c39b87c-a39c-413f-b1ef-07881195fcb8/osd-db-feee5095-b5e7-47a0-ae87-8e5039512661 db uuid Rtj5KA-Qxjk-IFmY-3ffQ-gSAu-Snte-uku8HC encrypted 0 osd fsid 2f009760-fc2b-46d5-984d-e8200dfd9d9d osd id 25 osdspec affinity osd_spec_wall type block vdo 0 with tpm 0 devices /dev/sdf [db] /dev/ceph-9c39b87c-a39c-413f-b1ef-07881195fcb8/osd-db-feee5095-b5e7-47a0-ae87-8e5039512661 block device /dev/ceph-23d9297a-d0e1-47be-8650-5c8ccae4fe0e/osd-block-2f009760-fc2b-46d5-984d-e8200dfd9d9d block uuid vqJGf8-V5g0-S1cA-BAcN-Qm9D-9VTx-xsc8wk cephx lockbox secret cluster fsid id cluster name ceph crush device class db device /dev/ceph-9c39b87c-a39c-413f-b1ef-07881195fcb8/osd-db-feee5095-b5e7-47a0-ae87-8e5039512661 db uuid Rtj5KA-Qxjk-IFmY-3ffQ-gSAu-Snte-uku8HC encrypted 0 osd fsid 2f009760-fc2b-46d5-984d-e8200dfd9d9d osd id 25 osdspec affinity osd_spec_wall type db vdo 0 with tpm 0 devices /dev/sde The other /dev/sde device did show up as data_device instead of db_device (example here on host2) : ceph-volume lvm list ====== osd.17 ====== [block] /dev/ceph-629f98b0-5ed4-4e75-81b9-e85ca76afb15/osd-block-5d43d683-1f7f-4dc1-935e-6a79745252f9 block device /dev/ceph-629f98b0-5ed4-4e75-81b9-e85ca76afb15/osd-block-5d43d683-1f7f-4dc1-935e-6a79745252f9 block uuid HQpp1l-x7IB-kA2W-6gWO-BGlM-VN2k-vYf43R cephx lockbox secret cluster fsid id cluster name ceph crush device class encrypted 0 osd fsid 5d43d683-1f7f-4dc1-935e-6a79745252f9 osd id 17 osdspec affinity osd_spec type block vdo 0 with tpm 0 devices /dev/sde Thx for your help Vivien