Managing HP Serviceguard A.11.20.10 for Linux, December 2012

MEMBER_TIMEOUT The amount of time, in microseconds, after which
Serviceguard declares that the node has failed and begins
re-forming the cluster without this node.
Default value: 14 seconds (14,000,000 microseconds).
This value leads to a failover time of between approximately
18 and 22 seconds, if you are using a quorum server, or
a Fiber Channel cluster lock, or no cluster lock. Increasing
the value to 25 seconds increases the failover time to
between approximately 29 and 39 seconds. The time will
increase by between 5 and 13 seconds if you are you using
a SCSI cluster lock or dual Fibre Channel cluster lock).
Maximum supported value: 300 seconds (300,000,000
microseconds).
If you enter a value greater than 60 seconds (60,000,000
microseconds), cmcheckconf and cmapplyconf will note
the fact, as confirmation that you intend to use a large value.
Minimum supported values:
• 3 seconds for a cluster with more than one heartbeat
subnet.
• 14 seconds for a cluster that has only one heartbeat
LAN
With the lowest supported value of 3 seconds, a failover
time of 4 to 5 seconds can be achieved.
NOTE: The failover estimates provided here apply to the
Serviceguard component of failover; that is, the package is
expected to be up and running on the adoptive node in this
time, but the application that the package runs may take
more time to start.
For most clusters that use a lock LUN, a minimum
MEMBER_TIMEOUT of 14 seconds is appropriate.
For most clusters that use a MEMBER_TIMEOUT value lower
than 14 seconds, a quorum server is more appropriate than
a lock LUN. The cluster will fail if the time it takes to acquire
the disk lock exceeds 0.2 times the MEMBER_TIMEOUT. This
means that if you use a disk-based quorum device (lock
LUN), you must be certain that the nodes in the cluster, the
connection to the disk, and the disk itself can respond
quickly enough to perform 10 disk writes within 0.2 times
the MEMBER_TIMEOUT.
Keep the following guidelines in mind when deciding how
to set the value.
Guidelines: You need to decide whether it's more important
for your installation to have fewer (but slower) cluster
re-formations, or faster (but possibly more frequent)
re-formations:
• To ensure the fastest cluster re-formations, use the
minimum value applicable to your cluster. But keep in
mind that this setting will lead to a cluster re-formation,
and to the node being removed from the cluster and
94 Planning and Documenting an HA Cluster