doc/cephfs: explain cephfs data and metadata set

Explain how to set application metadata for the CephFS data pool and the
CephFS metadata pool.

Signed-off-by: Zac Dover <zac.dover@proton.me>

diff --git a/doc/cephfs/nfs.rst b/doc/cephfs/nfs.rst
index 7b287bbc6ca66e1368bdcf14ff1cf67834bbeb3e..75e804e20f1bc6425202802624ff70cb4c0abd2c 100644 (file)
--- a/doc/cephfs/nfs.rst
+++ b/doc/cephfs/nfs.rst
@@ -56,6 +56,18 @@ in the sample conf. There are options to do the following:
 - enable read delegations (need at least v13.0.1 ``libcephfs2`` package
   and v2.6.0 stable ``nfs-ganesha`` and ``nfs-ganesha-ceph`` packages)
 
+.. important::
+
+   Under certain conditions, NFS access using the CephFS FSAL fails. This
+   causes an error to be thrown that reads "Input/output error". Under these
+   circumstances, the application metadata must be set for the CephFS metadata
+   and CephFS data pools. Do this by running the following command:
+
+   .. prompt:: bash $
+
+      ceph osd pool application set <cephfs_metadata_pool> cephfs <cephfs_data_pool> cephfs
+
+
 Configuration for libcephfs clients
 -----------------------------------