Managing Serviceguard A.11.20, March 2013

The Volume Monitor does not detect the following failures:
• Failure of a redundant link to a storage device or set of devices where a working link remains
• Failure of a mirror or mirrored plex within a volume (assuming at least one mirror or plex is
functional)
• Corruption of data on a monitored volume.
Planning for NFS-mounted File Systems
As of Serviceguard A.11.20, 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. It is now possible (as of A.11.20
April 2011 patch release) to create a Multi-Node Package that uses an NFS file share, and
this is useful if you want to create a HP Integrity Virtual Machine (HPVM) in a Serviceguard
Package, where the virtual machine itself uses a remote NFS share as backing store.
For details on how to configure NFS as a backing store for HPVM, see the HP Integrity Virtual
Machines 4.3: Installation, Configuration, and Administration guide at http://www.hp.com/
go/virtualization-manuals —> HP Integrity Virtual Machines and Online VM
Migration.
See Chapter 6 (page 232) 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 114).
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.
136 Planning and Documenting an HA Cluster