Managing Serviceguard Nineteenth Edition, Reprinted June 2011

IMPORTANT: Find out the MBTD value for each affected router and switch from the vendors'
documentation; determine all of the possible paths; find the worst case sum of the MBTD values
on these paths; and use the resulting value to set the Serviceguard
CONFIGURED_IO_TIMEOUT_EXTENSION parameter. For instructions, see the discussion of
this parameter under “Cluster Configuration Parameters ” (page 105).
Switches and routers that do not support MBTD value must not be used in a Serviceguard NFS
configuration. This might lead to delayed packets that in turn could lead to data corruption.
• Networking among the Serviceguard nodes must be configured in such a way that a single
failure in the network does not cause a package failure.
• Only NFS client-side locks (local locks) are supported.
Server-side locks are not supported.
• Because exclusive activation is not available for NFS-imported file systems, you should take
the following precautions to ensure that data is not accidentally overwritten.
◦ The server should be configured so that only the cluster nodes have access to the file
system.
◦ The NFS file system used by a package must not be imported by any other system,
including other nodes in the cluster. The only exception to this restriction is when you
want to use the NFS file system as a backing store for HPVM. In this case, the NFS file
system is configured as a multi-node package and is imported on more than one node
in the cluster.
◦ The nodes should not mount the file system on boot; it should be mounted only as part of
the startup for the package that uses it.
◦ The NFS file system should be used by only one package.
◦ While the package is running, the file system should be used exclusively by the package.
◦ If the package fails, do not attempt to restart it manually until you have verified that the
file system has been unmounted properly.
In addition, you should observe the following guidelines.
• CacheFS and AutoFS should be disabled on all nodes configured to run a package that uses
NFS mounts.
For more information, see the NFS Services Administrator's Guide HP-UX 11i version 3 at
http://www.hp.com/go/hpux-networking-docs.
• HP recommends that you avoid a single point of failure by ensuring that the NFS server is
highly available.
NOTE: If network connectivity to the NFS Server is lost, the applications using the imported
file system may hang and it may not be possible to kill them. If the package attempts to halt
at this point, it may not halt successfully.
• Do not use the automounter; otherwise package startup may fail.
• If storage is directly connected to all the cluster nodes and shared, configure it as a local file
system rather than using NFS.
• An NFS file system should not be mounted on more than one mount point at the same time.
• Access to an NFS file system used by a package should be restricted to the nodes that can
run the package.
For more information, see the white paper Using NFS as a file system type with Serviceguard
11.20 on HP-UX 11i v3 which you can find at http://www.hp.com/go/hpux-serviceguard-docs.
126 Planning and Documenting an HA Cluster