Managing HP Serviceguard A.11.20.20 for Linux, May 2013

4.5.1 Cluster Lock Requirements
A one-node cluster does not require a lock. Two-node clusters require the use of a cluster lock, and
a lock is recommended for larger clusters as well. Clusters larger than four nodes can use only a
quorum server as the cluster lock.
For information on configuring lock LUNs and the Quorum Server, see “Setting up a Lock LUN”
(page 143), section “Specifying a Lock LUN” (page 155), and HP Serviceguard Quorum Server
Version A.04.00, or later Release Notes at http://www.hp.com/go/hpux-serviceguard-docs (Select
HP Serviceguard Quorum Server Software).
4.5.2 Planning for Expansion
Bear in mind that a cluster with more than 4 nodes cannot use a lock LUN. So if you plan to add
enough nodes to bring the total to more than 4, you should use a quorum server.
4.5.3 Using a Quorum Server
The Quorum Server is described under “Use of the Quorum Server as a Cluster Lock” (page 41).
See also “Cluster Lock” (page 40).
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 support a cluster with any supported number of nodes.
• Can communicate with the cluster on up to two subnets (a primary and an alternate).
IMPORTANT: If you plan to use a Quorum Server, make sure you read the HP Serviceguard
Quorum Server Version A.04.00 Release Notes before you proceed. You can find them at http://
www.hp.com/go/hpux-serviceguard-docs (Select HP Serviceguard Quorum Server Software).. You
should also consult the Quorum Server white papers at the same location.
4.5.3.1 Quorum Server Worksheet
You can use the Quorum Server Worksheet (page 282) to identify a quorum server for use with one
or more clusters. You may want to record the following:
Quorum Server Host The host name for the quorum server.
IP Address The IP address(es) by which the quorum server will communicate
with the cluster nodes.
Supported Node Names The name (39 characters or fewer) of each cluster node that will
be supported by this quorum server. These entries will be entered
into qs_authfile on the system that is running the quorum server
process.
4.6 Volume Manager Planning
When designing your disk layout using LVM, you should consider the following:
• The volume groups that contain high availability applications, services, or data must be on a
bus or buses available to the primary node and all adoptive nodes.
• High availability applications, services, and data should be placed in volume groups that are
separate from non-high availability applications, services, and data.
• You must group high availability applications, services, and data, whose control needs to be
transferred together, on a single volume group or a series of volume groups.
4.6 Volume Manager Planning 85