Managing HP Serviceguard for Linux, Tenth Edition, September 2012

IMPORTANT: During Step 1, while the nodes are using a strict majority quorum, node
failures can cause the cluster to go down unexpectedly if the cluster has been using a
quorum device before the configuration change. For example, suppose you change the
quorum server polling interval while a two-node cluster is running. If a node fails during
Step 1, the cluster will lose quorum and go down, because a strict majority of prior cluster
members (two out of two in this case) is required. The duration of Step 1 is typically
around a second, so the chance of a node failure occurring during that time is very small.
In order to keep the time interval as short as possible, make sure you are changing only
the quorum configuration, and nothing else, when you apply the change.
If this slight risk of a node failure leading to cluster failure is unacceptable, halt the cluster
before you make the quorum configuration change.
How the Package Manager Works
Packages are the means by which Serviceguard starts and halts configured applications.
A package is a collection of services, disk volumes, IP addresses, and generic resources
that are managed by Serviceguard to ensure they are available.
Each node in the cluster runs an instance of the package manager; the package manager
residing on the cluster coordinator is known as the package coordinator.
The package coordinator does the following:
• Decides when and where to run, halt, or move packages.
The package manager on all nodes does the following:
• Executes the control scripts that run and halt packages and their services.
• Reacts to changes in the status of monitored resources.
Package Types
Three different types of packages can run in the cluster; the most common is the failover
package. There are also special-purpose packages that run on more than one node at
a time, and so do not fail over. They are typically used to manage resources of certain
failover packages.
Non-failover Packages
There are two types of special-purpose packages that do not fail over and that can run
on more than one node at the same time: the system multi-node package, which runs on
all nodes in the cluster, and the multi-node package, which can be configured to run on
all or some of the nodes in the cluster. System multi-node packages are reserved for use
by HP-supplied applications.
The rest of this section describes failover packages.
44 Understanding Serviceguard Software Components