Managing Serviceguard Eighteenth Edition, September 2010

Additional Heartbeat Requirements
VLAN technology allows great flexibility in network configuration. To maintain
Serviceguard’s reliability and availability in such an environment, the heartbeat rules
are tightened as follows when the cluster is using VLANs:
1. VLAN heartbeat networks must be configured on separate physical NICs or APA
aggregates, to avoid single points of failure.
2. Heartbeats are still recommended on all cluster networks, including VLANs.
3. If you are using VLANs, but decide not to use VLANs for heartbeat networks,
heartbeats are recommended for all other physical networks or APA aggregates
specified in the cluster configuration file.
Volume Managers for Data Storage
A volume manager is a tool that lets you create units of disk storage known as storage
groups. Storage groups contain logical volumes for use on single systems and in high
availability clusters. In Serviceguard clusters, storage groups are activated by package
control scripts.
Types of Redundant Storage
In Serviceguard, there are two types of supported shared data storage: mirrored
individual disks (also known as JBODs, for “just a bunch of disks”), and external disk
arrays which configure redundant storage in hardware. Two types of mirroring are
RAID1 and RAID5. Here are some differences between the two storage methods:
• If you are using JBODs, the basic element of storage is an individual disk. This
disk must be paired with another disk to create a mirror (RAID1). (Serviceguard
configurations usually have separate mirrors on different storage devices).
• If you have a disk array, the basic element of storage is a LUN, which already
provides storage redundancy via hardware RAID1 or RAID5.
About Device File Names (Device Special Files)
HP-UX releases up to and including 11i v2 use a naming convention for device files
that encodes their hardware path. For example, a device file named /dev/dsk/
c3t15d0 would indicate SCSI controller instance 3, SCSI target 15, and SCSI LUN 0.
HP-UX 11i v3 introduces a new nomenclature for device files, known as agile
addressing (sometimes also called persistent LUN binding).
Under the agile addressing convention, the hardware path name is no longer encoded
in a storage device’s name; instead, each device file name reflects a unique instance
number, for example /dev/[r]disk/disk3, that does not need to change when the
hardware path does.
Agile addressing is the default on new 11i v3 installations, but the I/O subsystem still
recognizes the pre-11.i v3 nomenclature. This means that you are not required to convert
106 Understanding Serviceguard Software Components