Using NFS as a filesystem type with HP Serviceguard A.11.20 on HP-UX 11i v3, September 2010

To prevent this, you must determine a maximum delay between when a write is issued from any

Serviceguard node and when it can arrive at the NFS server. Use the discussion that follows for

guidance.

The NFS write may go through network switches before it reaches the NFS server. In each switch, the

packet will be dropped after some specific time has elapsed. The IEEE Bridge specification, 802.1D,

refers to this value as ‘Maximum Bridge Transit Delay’ (MBTD).

IMPORTANT:

All switches and routers that are configured between the NFS server and

Serviceguard nodes must support MBTD.

You can calculate the lifetime of an NFS client’s write packet by adding the MBTD value of all the

switches and routers that are configured between the NFS server and the Serviceguard nodes.

You must set the Serviceguard cluster parameter CONFIGURED_IO_TIMEOUT_EXTENSION for any

cluster in which packages use NFS mounts. See the section on cluster configuration parameters in

chapter 4 of the Managing Serviceguard manual for more information about

CONFIGURED_IO_TIMEOUT_EXTENSION.

To set the value for the CONFIGURED_IO_TIMEOUT_EXTENSION, first determine MBTD

for each switch and router. The value should be in the vendors' documentation. Set the

CONFIGURED_IO_TIMEOUT_EXTENSION to the sum of the values for the switches and routers.

If there is more than one possible path between the NFS server and the cluster nodes, sum the values

for each path and use the largest number.

The CONFIGURED_IO_TIMEOUT_EXTENSION value will be greater the more routers and switches

there are between the NFS server and Serviceguard nodes. The cluster reformation time is increased

by the CONFIGURED_IO_TIMEOUT_EXTENSION, so keep this value as low as possible by

appropriate routing between the NFS server and Serviceguard nodes or by using hardware that

supports smaller MBTD values.

The CONFIGURED_IO_TIMEOUT_EXTENSION parameter must also be set in some cases in an

extended-distance cluster (EDC); see the discussion of this parameter in Managing Serviceguard for

details. If packages use NFS imports in an EDC, calculate the settings for each case separately (that

is, the value required for the EDC configuration, and the value required for NFS) and use the greater

of the two values.

For example, if the EDC configuration requires CONFIGURED_IO_TIMEOUT_EXTENSION to be

1000000 (microseconds) and the NFS configuration requires it to be 2000000, set it to 2000000.

In the example in Figure 1, with only one switch between the NFS server and the NFS client, set the

CONFIGURED_IO_TIMEOUT_EXTENSION to the MBTD value of the switch in microseconds. In this

case is the MBTD of the switch is 1 second, so set CONFIGURED_IO_TIMEOUT_EXTENSION

to 1000000.