Reference Guide

Introduction 7
Introduction
Clustering uses specific hardware and software to join multiple systems
together to function as a single system and provide an automatic failover
solution. If one of the clustered systems (also known as cluster nodes, or
nodes) fails, resources running on the failed system are moved (or failed over)
to one or more systems in the cluster by the Microsoft
®
Cluster Service (MSCS)
software. MSCS is the failover software component in specific versions of the
Windows
®
operating system.
When the failed system is repaired and brought back online, resources
automatically transfer back (or fail back) to the repaired system or remain on
the failover system, depending on how MSCS is configured. For more
information, see "Configuring Active and Passive Cluster Nodes" on page 46.
NOTE: Reference to Microsoft Windows Server
®
2003 in this guide implies reference
to Windows Server 2003 Enterprise Edition, Windows Server 2003 R2 Enterprise Edition,
Windows Server 2003 Enterprise x64 Edition, and Windows Server 2003 R2 Enterprise
x64 Edition unless explicitly stated.
Virtual Servers and Resource Groups
In a cluster environment, users do not access a physical server; they access a
virtual server, which is managed by MSCS. Each virtual server has its own
IP address, name, and hard drive(s) in the shared storage system. MSCS manages
the virtual server as a resource group, which contains the cluster resources.
Ownership of virtual servers and resource groups is transparent to users. For
more information on resource groups, see "Cluster Resources" on page 39.
When MSCS detects a failed application that cannot restart on the same
server node or a failed server node, MSCS moves the failed resource group(s)
to one or more server nodes and remaps the virtual server(s) to the new
network connection(s). Users of an application in the virtual server experience
only a momentary delay in accessing resources while MSCS re-establishes a
network connection to the virtual server and restarts the application.