Managing Serviceguard 14th Edition, June 2007

Building an HA Cluster Configuration
Preparing Your Systems
Chapter 5214
Backing Up Cluster Lock Disk Information
After you configure the cluster and create the cluster lock volume group
and physical volume, you should create a backup of the volume group
configuration data on each lock volume group. Use the vgcfgbackup
command for each lock volume group you have configured, and save the
backup file in case the lock configuration must be restored to a new disk
with the vgcfgrestore command following a disk failure.
NOTE You must use the vgcfgbackup and vgcfgrestore commands to back up
and restore the lock volume group configuration data regardless of how
you create the lock volume group.
Setting Up a Lock LUN
LUN stands for Logical Unit Number. The term can refer to a single
physical disk, but these days is more often used in a SAN (Storage Area
Network) or NAS (Network-Attached Storage) context to denote a virtual
entity derived from one or more physical disks.
Keep the following points in mind when choosing a device for a lock
LUN:
• All the cluster nodes must be physically connected to the lock LUN.
• All existing data on the LUN will be destroyed when you configure it
as a lock LUN.
This means that if you use an existing lock disk, the existing lock
information will be lost, and if you use a LUN that was previously
used as a lock LUN for a Linux cluster, that lock information will
also be lost.
• A lock LUN cannot also be used in an LVM physical volume or VxVM
or CVM disk group.
• A lock LUN cannot be shared by more than one cluster.
• A lock LUN cannot be used in a dual-lock configuration.
• You do not need to back up the lock LUN data, and in fact there is no
way to do so.
A lock LUN needs only a small amount of storage, about 100 KB.