I follow below document to setup image level rbd persistent cache, however I get error output while i using the command provide by the document. I have put my commands and descriptions below. Can anyone give some instructions? thanks in advance. https://docs.ceph.com/en/pacific/rbd/rbd-persistent-write-back-cache/ https://access.redhat.com/documentation/en-us/red_hat_ceph_storage/5/html/bl... [https://access.redhat.com/webassets/avalon/g/shadowman-200.png]<https://access.redhat.com/documentation/en-us/red_hat_ceph_storage/5/html/block_device_guide/ceph-block-devices#enabling-persistent-write-log-cache_block> Chapter 2. Ceph block devices Red Hat Ceph Storage 5 | Red Hat Customer Portal<https://access.redhat.com/documentation/en-us/red_hat_ceph_storage/5/html/block_device_guide/ceph-block-devices#enabling-persistent-write-log-cache_block> Access Red Hat’s knowledge, guidance, and support through your subscription. access.redhat.com I tried use host level client command, i got no error, however I won't be able to get cache usage output. "ceph config set client rbd_persistent_cache_mode ssd ceph config set client rbd_plugins pwl_cache" [root@master-node1 ceph]# rbd info sas-pool/testdrive rbd image 'testdrive': size 40 GiB in 10240 objects order 22 (4 MiB objects) snapshot_count: 0 id: 3de76a7e7c519 block_name_prefix: rbd_data.3de76a7e7c519 format: 2 features: layering, exclusive-lock, object-map, fast-diff, deep-flatten op_features: flags: create_timestamp: Thu Jun 29 02:03:41 2023 access_timestamp: Thu Jun 29 07:19:40 2023 modify_timestamp: Thu Jun 29 07:18:00 2023 I check feature exclusive-lock has been already enabled and I run following command get fault output. [root@master-node1 ceph]# rbd config image set sas-pool/testdrive rbd_persistent_cache_mode ssd rbd: invalid config key: rbd_persistent_cache_mode [root@master-node1 ceph]# rbd config image set sas-pool/testdrive rbd_plugins pwl_cache rbd: invalid config key: rbd_plugins root@node1:~# rbd status sas-pool/testdrive Watchers: watcher=10.1.254.51:0/1544956346 client.39553300 cookie=140244238214096 I hope to see the output include the persistent cache state like below: $ rbd status rbd/foo Watchers: watcher=10.10.0.102:0/1061883624 client.25496 cookie=140338056493088 Persistent cache state: host: sceph9 path: /mnt/nvme0/rbd-pwl.rbd.101e5824ad9a.pool size: 1 GiB mode: ssd stats_timestamp: Sun Apr 10 13:26:32 2022 present: true empty: false clean: false allocated: 509 MiB cached: 501 MiB dirty: 338 MiB free: 515 MiB hits_full: 1450 / 61% hits_partial: 0 / 0% misses: 924 hit_bytes: 192 MiB / 66% miss_bytes: 97 MiB