Managing HP Serviceguard for Linux, Eighth Edition, March 2008

Understanding Serviceguard Software Components
Volume Managers for Data Storage
Chapter 3 83
Volume Managers for Data Storage
A volume manager is a tool that lets you create units of disk storage that
are more flexible than individual disk partitions. These units can be used
on single systems or in high availability clusters. HP Serviceguard for
Linux uses the Linux Logical Volume Manager (LVM) which creates
redundant storage groups. This section provides an overview of volume
management with LVM. Refer to the section on “Creating the Logical
Volume Infrastructure” in Chapter 5 for details about configuring
volume groups, logical volumes, and file systems for use in Serviceguard
packages.
In HP Serviceguard for Linux, the supported shared data storage type is
disk arrays which configure redundant storage in hardware.
In a disk array, the basic element of storage is a LUN, which already
provides storage redundancy via RAID1 or RAID5. Before you can use
the LUNs, you must partition them using fdisk.
In LVM, you manipulate storage in one or more volume groups. A
volume group is built by grouping individual physical volumes.
Physical volumes can be disk partitions or LUNs that have been marked
as physical volumes as described below.
You use the pvcreate command to mark the LUN as physical volumes.
Then you use the vgcreate command to create volume groups out of one
or more physical volumes. Once configured, a volume group can be
subdivided into logical volumes of different sizes and types. File
systems or databases used by the applications in the cluster are mounted
on these logical volumes. In Serviceguard clusters, volume groups are
activated by package control scripts when an application starts up, and
they are deactivated by package control scripts when the application
halts.