VERITAS Volume Manager 3.5 Installation Guide (August 2002)

Installation and Upgrade Requirements

12 VERITAS Volume Manager Installation Guide

Cluster Environment Requirements

If your conﬁguration has a cluster, which is a set of hosts that share a set of disks, follow

these steps:

1. Obtain a license for the optional VxVM cluster feature from your Customer Support

channel.

2. Decide where to place the rootdg disk group for each node in the cluster. A system

using VxVM has one or more disk groups, including the rootdg. The rootdg must

exist, and it cannot be sharedbetween systems.At leastone diskmust existwithin the

rootdg while VxVM is running.

3. Decide on the layout of shared disk groups. There may be one or more shared disk

groups. Determine how many you wish to use.

4. If you plan to use Dirty Region Logging (DRL) with VxVM in a cluster, leave a small

amount of space on the disk for these logs. The log size is proportional to the volume

size and thenumber ofnodes. Each log hasone recovery map plusone activemap per

node.

For a two-gigabyte volume in a two-node cluster, a log size of three blocks (one block

per map) is sufﬁcient. For every additional two gigabytes of volume size, the log size

increases by approximately one block per map (for example, a four-gigabyte volume

with two nodes has a log size of six blocks) up to a maximum of 96 blocks. For larger

volumes, DRL changesthelog granularitytoaccommodate theincreasedsizewithout

exceeding the maximum log size. A four-node cluster requires larger logs.

5. Refer to the VERITAS Volume Manager Administrator’s Guide for more information on

DRL.