VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

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Administering Cluster Functionality

Introduction

A cluster consists of a number ofhosts or nodes that share a set of disks. The mainbeneﬁts

of cluster conﬁgurations are:

◆ Availability—If one node fails, the other nodes can still access the shared disks. When

conﬁgured with suitable software, mission-critical applications can continue running

by transferring their execution to a standby node in the cluster. This ability to provide

continuous uninterrupted service by switching to redundant hardware is commonly

termed failover.

Failover is transparent to users and high-level applications for database and

ﬁle-sharing. You must conﬁgure cluster management software to monitor systems

and services, and to restart applications on another node in the event of either

hardware or software failure.

◆ Off-host processing—Clusters can reduce contention for system resources by

performing activities such as backup, decision support and report generation on the

more lightly loaded nodes of the cluster. This allows businesses to derive enhanced

value from their investment in cluster systems.

The cluster functionality of VERITAS Volume Manager (VxVM) allowsup to16 nodesin a

cluster to simultaneously access and manage a set of disks under VxVM control (VM

disks). The same logical view of disk conﬁguration and any changes to this is available on

all the nodes. When the cluster functionality is enabled, all the nodes in the cluster can

share VxVM objects. This chapter discusses the cluster functionality that is provided with

VxVM.

Note You need an additional license to use this feature.

This chapter does not discuss VERITAS Cluster File System

nor cluster management

software. See the documentation provided with these products for more information

about them.

For additional information about using the Dynamic Multipathing (DMP) feature of

VxVM in a clustered environment, see “DMP in a Clustered Environment” on page 104.