Managing HP Serviceguard A.11.20.10 for Linux, December 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.
3.3 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, generic resources , and IP addresses, 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.
3.3.1 Package Types
Three different types of packages can run in the cluster; the most common is the failoverpackage.
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.
3.3.1.1 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.
3.3.1.2 Failover Packages
A failover package starts up on an appropriate node (see node_name (page 170)) when the cluster
starts. In the case of a service, network, or other resource or dependency failure, package failover
takes place. A package failover involves both halting the existing package and starting the new
instance of the package on a new node.
Failover is shown in the following figure:
3.3 How the Package Manager Works 41