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.
 | Tip |
|---|
| | 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. |
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.
