|Red Hat Cluster Suite: Configuring and Managing a Cluster|
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The following points should be taken into consideration when clustered NFS services are configured.
File systems being NFS exported by cluster members do not get specified in the conventional /etc/exports file. Rather, the NFS exports associated with cluster services are specified in the cluster configuration file (as established by the Cluster Configuration Tool).
The command exportfs -r removes any exports which are not explicitly specified in the /etc/exports file. Running this command causes the clustered NFS services to become unavailable until the service is restarted. For this reason, it is recommended to avoid using the exportfs -r command on a cluster on which highly available NFS services are configured. To recover from unintended usage of exportfs -r, the NFS cluster service must be stopped and then restarted.
NFS file locks are not preserved across a failover or service relocation. This is due to the fact that the Linux NFS implementation stores file locking information in system files. These system files representing NFS locking state are not replicated across the cluster. The implication is that locks may be regranted subsequent to the failover operation.