Serviceguard NFS Toolkit A.11.11.06, A.11.23.05 and A.11.31.03 Administrator's Guide

1 Overview of Serviceguard NFS
Serviceguard NFS is a tool kit that enables you to use Serviceguard to set up highly available
NFS servers.
You must set up a Serviceguard cluster before you can set up Highly Available NFS. For
instructions on setting up a Serviceguard cluster, see the Managing Serviceguard manual.
Serviceguard NFS is a separately purchased set of configuration files and control script, which
you customize for your specific needs. These files, once installed, are located in /opt/
cmcluster/nfs.
Serviceguard allows you to create high availability clusters of HP 9000 Series 800 computers on
HP-UX 11i v1 and HP-UX 11i v2 systems. On HP-UX 11i v3 systems, clusters may comprise of
both HP Integrity servers and HP 9000 Series 800 computers. A high availability computer system
allows applications to continue in spite of a hardware or software failure. Serviceguard systems
protect users from software failures as well as from failure of a system processing unit (SPU) or
local area network (LAN) component. In the event that one component fails, the redundant
component takes over, and Serviceguard coordinates the transfer between components.
An NFS server is a host that exports its local directories (makes them available for client hosts
to mount using NFS). On the NFS client, these mounted directories look to users like part of the
client's local file system.
With Serviceguard NFS, the NFS server package containing the exported file systems can move
to a different node in the cluster in the event of failure. After Serviceguard starts the NFS package
on the adoptive node, the NFS file systems are re-exported from the adoptive node with minimum
disruption of service to users. The client side hangs until the NFS server package comes up on
the adoptive node. When the service returns, the user can continue access to the file. You do not
need to restart the client.
Limitations of Serviceguard NFS
The following limitations apply to Serviceguard NFS:
• Applications lose their file locks when an NFS server package moves to a new node.
Therefore, any application that uses file locking must reclaim its locks after an NFS server
package fails over.
An application that loses its file lock due to an NFS package failover does not receive any
notification. If the server is also an NFS client, it loses the NFS file locks obtained by client-side
processes.
NOTE: Beginning with Serviceguard NFS A.11.11.03 and A.11.23.02, you can address this
limitation by enabling the File Lock Migration feature (see “Overview of the NFS File Lock
Migration Feature” (page 8)).
For HP-UX 11i v2 and 11i v3, the feature functions properly without a patch.
• If a server is configured to use NFS over TCP and the client is the same machine as the server,
which results in a loopback NFS mount, the client may hang for about 5 minutes if the
package is moved to another node. The solution is to use NFS over UDP between
NFS-HA-server cross mounts.
• The /etc/rmtab file is not synchronized when an NFS package fails over to the standby
node. This is caused by the design of NFS, which does not keep track of the state of the
rmtab. The man page for rmtab contains a warning that it is not always totally accurate,
so it is also unreliable in a standard NFS server / NFS client environment.
• AutoFS mounts may fail when mounting file systems exported by an HA-NFS package soon
after that package has been restarted. To avoid these mount failures, AutoFS clients should
Limitations of Serviceguard NFS 7