1.4. Shared File Systems service with CephFS through NFS fault tolerance
When Red Hat OpenStack Platform (RHOSP) director starts the Ceph service daemons, they manage their own high availability (HA) state and, in general, there are multiple instances of these daemons running. By contrast, in this release, only one instance of NFS-Ganesha can serve file shares at a time.
To avoid a single point of failure in the data path for CephFS through NFS shares, NFS-Ganesha runs on a RHOSP Controller node in an active-passive configuration managed by a Pacemaker-Corosync cluster. NFS-Ganesha acts across the Controller nodes as a virtual service with a virtual service IP address.
If a Controller node fails or the service on a particular Controller node fails and cannot be recovered on that node, Pacemaker-Corosync starts a new NFS-Ganesha instance on a different Controller node using the same virtual IP address. Existing client mounts are preserved because they use the virtual IP address for the export location of shares.
Using default NFS mount-option settings and NFS 4.1 or later, after a failure, TCP connections are reset and clients reconnect. I/O operations temporarily stop responding during failover, but they do not fail. Application I/O also stops responding but resumes after failover completes.
New connections, new lock-state, and so on are refused until after a grace period of up to 90 seconds during which time the server waits for clients to reclaim their locks. NFS-Ganesha keeps a list of the clients and exits the grace period earlier if all clients reclaim their locks.
The default value of the grace period is 90 seconds. To change this value, edit the NFSv4
Grace_Period configuration option.