doc/man/rbd: resurrect filestore alloc_size note

Mistakenly removed in commit d79f2a81541c ("docs: warning and remove
few docs section for Filestore Update docs after filestore removal.").
The kernel client, however new, will continue to be able to talk to
FileStore OSDs for as long as they exist.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/doc/man/8/rbd.rst b/doc/man/8/rbd.rst
index a46429d9b2f5a62e77e0edbdc3acf76ffec8f64e..59e3462097530ea38c7fc967bd60b28e81ceb112 100644 (file)
--- a/doc/man/8/rbd.rst
+++ b/doc/man/8/rbd.rst
@@ -831,7 +831,8 @@ Per mapping (block device) `rbd device map` options:
   drop discards that are too small.  For bluestore, the recommended setting is
   bluestore_min_alloc_size (currently set to 4K for all types of drives,
   previously used to be set to 64K for hard disk drives and 16K for
-  solid-state drives).
+  solid-state drives).  For filestore with filestore_punch_hole = false, the
+  recommended setting is image object size (typically 4M).
 
 * crush_location=x - Specify the location of the client in terms of CRUSH
   hierarchy (since 5.8).  This is a set of key-value pairs separated from