Managing HP Serviceguard A.11.20.00 for Linux, June 2012

For information about creating, exporting, and importing volume groups, see “Creating the Logical
Volume Infrastructure ” (page 130).
Planning for NFS-mounted File Systems
As of Serviceguard A.11.20.00, you can use NFS-mounted (imported) file systems as shared
storage in packages.
The same package can mount more than one NFS-imported file system, and can use both cluster-local
shared storage and NFS imports.
The following rules and restrictions apply.
• NFS mounts are supported for modular failover packages.
• So that Serviceguard can ensure that all I/O from a node on which a package has failed is
flushed before the package restarts on an adoptive node, all the network switches and routers
between the NFS server and client must support a worst-case timeout, after which packets and
frames are dropped. This timeout is known as the Maximum Bridge Transit Delay (MBTD).
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 80).
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 must take the
following precautions to ensure that data is not accidentally overwritten.
◦ The server must 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 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 on NFS in HP-UX, 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.
94 Planning and Documenting an HA Cluster