Managing Serviceguard Eighteenth Edition, September 2010

The following rules and restrictions apply.
NFS mounts are supported only for modular, failover packages.
See Chapter 6 (page 279) for a discussion of types of 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 143).
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 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.
Package Configuration Planning 175