Managing Serviceguard Sixteenth Edition, March 2009

four nodes can use only a quorum server as the cluster lock. In selecting a cluster lock
configuration, be careful to anticipate any potential need for additional cluster nodes.
For more information on lock disks, lock LUNs, and the Quorum Server, see “Choosing
Cluster Lock Disks” (page 202), “Setting Up a Lock LUN” (page 202), and “Setting Up
and Running the Quorum Server” (page 206).
Cluster Lock Disk and Re-formation Time
cmquerycl displays the failover time for the cluster in the Possible Cluster
Lock Devices section, for example:
Possible Cluster Lock Devices:
/dev/dsk/c0t1d4 30 seconds
Note: all lock disks have the same failover time
All disks in all volume groups which are accessible by all nodes in the cluster are
potential cluster lock devices, but because it takes a fixed amount of time to acquire
the cluster lock, regardless of the lock device, only the first potential lock device is
displayed. You may need to choose a different device because of power considerations;
see “Power Supply Planning ” (page 130).
Planning for Expansion
Bear in mind that a cluster with more than 4 nodes cannot use a lock disk or lock LUN.
Thus, if you plan to add enough nodes to bring the total to more than 4, you should
use a quorum server.
Using a Quorum Server
The operation of Quorum Server is described under “Use of the Quorum Server as the
Cluster Lock” (page 65). See also “Cluster Lock ” (page 62).
A quorum server:
• Can be used with up to 150 clusters, not exceeding 300 nodes total.
• Can support a cluster with any supported number of nodes.
• Can communicate with the cluster on up to two subnets (a primary and an alternate)
using either IPv4 or IPv6 addresses.
132 Planning and Documenting an HA Cluster