Managing HP Serviceguard A.12.00.00 for Linux, June 2014

NOTE: Ensure that the NFS module is loaded during boot time for the configurations using NFS
file systems as part of the package configuration.
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 89).
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.
• 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.
4.9 Package Configuration Planning 105