Managing Serviceguard Seventeenth Edition, First Reprint December 2009
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.
• A lock LUN must be a block device.
• 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.
• If you are using a disk array, create the smallest LUN the array will allow, or, on
an HP Integrity server, you can partition a LUN; see “Creating a Disk Partition on
an HP Integrity System”.
• If you are using individual disks, use either a small disk, or a portion of a disk. On
an HP Integrity server, you can partition a disk; see “Creating a Disk Partition on
an HP Integrity System”.
206 Building an HA Cluster Configuration