2.2. Clusters

This section describes how to create, activate and manage host clusters in a data center.
A cluster is a collection of physical hosts that share the same storage domains and have the same type of CPU. Because virtual machines can be migrated across hosts in the same cluster, the cluster is the highest level at which power and load-sharing policies can be defined. The Red Hat Enterprise Virtualization platform contains a default cluster in the default data center at installation.
Cluster

Figure 2.8. Cluster


Each cluster is a logical group that consists of multiple hosts. Every cluster in the system must belong to a data center, and every host in the system must belong to a cluster. This enables the system to dynamically allocate a virtual machine to any host in the applicable cluster, according to policies defined on the Clusters tab and in the Configuration tool during runtime, thus maximizing memory and disk space, as well as virtual machine uptime.
At any given time, after a virtual machine runs on a specific host in the cluster, the virtual machine can be migrated to another host in the cluster using Migrate. This can be very useful when a host is shut down for maintenance. The migration to another host in the cluster is transparent to the user, and the user continues working as usual. Note that a virtual machine cannot be migrated to a host outside the cluster.

2.2.1. Cluster Properties

Clusters can be defined, managed and viewed using the Clusters tab on the Red Hat Enterprise Virtualization Manager Administration Portal.
Clusters Tab

Figure 2.9. Clusters Tab


The table below describes the properties of a cluster as displayed in the New Cluster and Edit Cluster dialog boxes under General. Missing mandatory fields and invalid entries are outlined in red when you click OK to close the dialog box. In addition, field prompts indicate the expected values or range of values.

Table 2.6. Cluster Properties

Field/Tab
Description/Action
Data Center
The name of the data center. This must be a unique name with any combination of uppercase or lowercase letters, numbers, hyphens and underscores. Maximum length is 40.
Name
The name of the cluster. This must be a unique name with any combination of uppercase or lowercase letters, numbers, hyphens and underscores. Maximum length is 40.
Description
The description of the cluster. While this is not a mandatory field, it is recommended.
Type
Any one of, Intel or AMD. This cannot be changed after creation without significant disruption and high possibility of data loss. The type of data domain dictates the type of the data center.
Compatibility Level
The version of the Red Hat Enterprise Virtualization, either 2.2 or 3.0.