Managing Serviceguard Eighteenth Edition, September 2010

Server), the quorum device (for example from one quorum server to another), and the
parameters that govern them (for example the Quorum Server polling interval). For
more information about the Quorum Server and lock parameters, see “Cluster
Configuration Parameters ” (page 143).
NOTE: If you are using the Veritas Cluster Volume Manager (CVM) you cannot
change the quorum configuration while SG-CFS-pkg is running. For more information
about CVM, see “CVM and VxVM Planning ” (page 134).
When you make quorum configuration changes, Serviceguard goes through a two-step
process:
1. All nodes switch to a strict majority quorum (turning off any existing quorum
devices).
2. All nodes switch to the newly configured quorum method, device and parameters.
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 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.
How the Package Manager Works 67