HP ProLiant DL380G5-WSS 3.7.0 HP StorageWorks HP Scalable NAS File Serving Sof - Page 165
Caveats regarding Export Groups, Mount PSFS filesystems
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If a failure occurs on the server to which NFS clients are connected or the server loses access to the PSFS filesystem (for example, because of a SAN problem), the appropriate monitor probe will report the failure. The Virtual NFS Services active on that server are then failed over (redirected) to a backup server. Failover is transparent to the NFS clients; their access to the exported filesystems continues after a brief pause. Caveats regarding Export Groups Before creating an Export Group, you should be aware of the following: • Although you can configure multiple Export Group files, with each group having its own set of export records, all of the export records are ultimately merged into a single /etc/exports file that is automatically installed on each node in the cluster. Because an export can be included in more than one Export Group, the /etc/exports file can contain multiple records referring to the same filesystem path to be exported. If these duplicate records specify different export options, it is indeterminate which options the NFS service will assume. It is therefore recommended that any given filesystem subtree be exported by at most one Export Group. • Although an Export Group can specify that only certain nodes can export its filesystems, the contents of the Export Group are available via the /etc/exports file on every node in the cluster. This means that users can access the exported filesystems from nodes where the Export Group is not defined by connecting via the physical address of the node. However, such access is not highly available because there is no Virtual NFS Service associated with those connections. This is not a security concern because the entire cluster should be considered as a single security domain (for this and other reasons). The administrator can track which nodes are exporting highly available NFS services by watching the Export Group high-availability monitors that are active on those nodes. Mount PSFS filesystems Before configuring Export Groups, ensure that the filesystems to be exported are on PSFS filesystems and are mounted on all the pertinent nodes with the "persist" mount option. The Cluster Coherent Record Locks mount option should not be disabled on filesystems that will be exported. (Setting the command-line localbrlocks mount option also disables cluster-coherent record locks.) NFS lock acquisitions will not work on filesystems mounted with cluster-coherent record locks disabled. See Chapter 8, page 121 for details about creating and mounting PSFS filesystems. HP Scalable NAS File Serving Software administration guide 165