Describe the issue:
"rwl" mode (PMEM devices) is included in RHCS 5.0 as a Tech Preview/Headliner: 

The following content/settings need to be documented:
+rbd persistent cache mode = rwl needs to be documented
+overview context
+cache configuration setting settings 
+rbd status {pool-name}/{image-name} 
+rbd image-cache invalidate {pool-name}/{image-name}
+rbd plugins = pwl_cache 

https://docs.ceph.com/en/latest/rbd/rbd-persistent-write-back-cache/#enable-persistent-write-back-cache

Additional information:
rbd persistent cache mode = ssd is NOT part of 5.0 (target 5.1) and is not to be documented for this BZ.