Mount 5 Error

A mount 5 error typically occurs if a MDS server is laggy or if it crashed. Ensure at least one MDS is up and running, and the cluster is active + healthy.

Mount 12 Error

A mount 12 error with cannot allocate memory usually occurs if you have a version mismatch between the Ceph Client version and the Ceph Storage Cluster version. Check the versions using:

ceph -v

If the Ceph Client is behind the Ceph cluster, try to upgrade it:

sudo apt-get update && sudo apt-get install ceph-common

You may need to uninstall, autoclean and autoremove ceph-common and then reinstall it so that you have the latest version.