IBM Netfinity ServeRAID-4H Ultra160 User Reference Download Page 87

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Chapter 5. Preparing to install or change a cluster solution

Note: If you are going to upgrade an existing high-availability cluster solution and

are already familiar with the concepts of a cluster, go to “Chapter 6. Updating
the ServeRAID BIOS, firmware, and software code” on page 77. If you are
setting up your first high-availability cluster solution, continue reading this
section.

Before you begin installing and setting up a high-availability cluster solution, it is
important to familiarize yourself with the following terms and definitions that are
used in this manual, as well as some considerations concerning the ServeRAID
controller.

Note: The following terms and definitions are for the Microsoft Cluster Service

using Windows NT or Windows 2000. For similar terms and definitions for
the Novell IntranetWare Cluster Solution using Novell NetWare, refer to the
Vinca High Availability for NetWare manual.

Terms and definitions

The following terms are used in this manual:

Failover is the process of relocating the cluster resources from a failed server to
the surviving server. The resource-monitor program responsible for the resource
detects the failure. If a resource failure occurs, the resource-monitor program
notifies the Cluster Service, which triggers the actions that are defined in the
failover policy for that resource. A failover can occur automatically, such as when an
application or a server fails, or it can occur manually, such as when a system
administrator moves all applications onto one server and then brings the other
server down for scheduled maintenance. Failover generally consists of three
components:

Failure detection

Resource relocation

Application restart.

Failback is a special case of failover and is the process of moving back some or all
groups of resources to the preferred owner after a failover has occurred. The
preferred owner is the server in the cluster on which you prefer each group of
resources to run. If the preferred owner fails, its resources are transferred to the
other server. When the preferred owner is repaired and comes back online, and
allow failback is enabled in the Microsoft Cluster Administration program, the
resources are automatically transferred back to that server.

Resource Group is dependent resources that can be grouped together. Some
resources need other resources to run successfully and are known as resource
dependencies. When one resource is listed as a dependency for another resource,
the two resources must be placed in the same group. If all resources are ultimately
dependent on one resource (for example, one physical disk resource), all resources
must be in the same group. Therefore, all resources in a cluster might need to be in
the same group.

Also, any cluster operation performed on a group is performed on all resources that
are in that group. For example, if a resource must be moved from Server A to
Server B, all resources that are in the same group as the resource will be moved
also.