A failover domain is a named subset of cluster members that are
eligible to run a cluster service in the event of a system failure.
A failover domain can have the following characteristics:
-
Unrestricted — Allows you to specify that a subset of
members are preferred, but that a cluster service assigned to this
domain can run on any available member.
-
Restricted — Allows you to restrict the members that can
run a particular cluster service. If none of the members in a
restricted failover domain are available, the cluster service
cannot be started (either manually or by the cluster software).
-
Unordered — When a cluster service is assigned to an
unordered failover domain, the member on which the cluster service
runs is chosen from the available failover domain members with no
priority ordering.
-
Ordered — Allows you to specify a preference order among
the members of a failover domain. The member at the top of the list
is the most preferred, followed by the second member in the list,
and so on.
By default, failover domains are unrestricted and unordered.
In a cluster with several members, using a restricted failover
domain can minimize the work to set up the cluster to run a cluster
service (such as httpd, which requires
you to set up the configuration identically on all members that run
the cluster service). Instead of setting up the entire cluster to
run the cluster service, you must set up only the members in the
restricted failover domain that you associate with the cluster
service.
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To implement the concept of a preferred member, create an
unrestricted failover domain comprised of only one cluster member.
By doing this, a cluster service runs on the preferred member; in
the event of a failure, the cluster service fails over to any of
the other members.
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To add a failover domain to the cluster software configuration,
follow these steps:
-
Select the Failover Domains property and
click the Create a Failover Domain button.
The Failover Domain dialog box is displayed
prompting you to create a name for the domain. Enter a name for the
domain and click OK, which then displays the Failover Domain Configuration dialog.
-
In the Failover Domain Configuration
dialog box (shown in Figure
3-9), there are several options available to customize the
failover domain for your resource and/or service.
Enter a name for the domain in the Domain
Name field. The name should be descriptive enough to
distinguish its purpose relative to other names used on your
network.
-
Click Available Cluster Nodes drop-down
to select the members for this failover domain.
-
Check Restrict Failover To This Domains
Members to prevent any member other than those listed from
taking over a cluster service assigned to this domain.
-
Check Prioritized List if you want
members to assume control of a failed cluster service in a
particular order. Click the Adjust
Priorities arrows to configure order of the nodes in the
domain. Preference is indicated by the member's position in the
list of members in the domain, with the most preferred member given
the higher priority value.
-
Click Close to create the domain.
-
Choose => to save the changes to the cluster
configuration.
To remove a member from a failover domain, follow these
steps:
-
On the Failover Domains property, click
the name of the domain you want to modify (or select the domain and
click Edit Failover Domain
Properties).
-
In the Failover Domain Configuration
dialog box, click the name of the member you want to remove from
the domain and click Remover Member from
Domain. (Members must be deleted one at a time.)
-
When finished, click OK.
-
Choose => to save the changes to the cluster
configuration.
