Failover Cluster Installation and Configuration Guide, Windows Server 2008 SP2 and Windows Server 2008 R2 SP1

cluster will come online as long as a majority of votes are reached, regardless of the status of the
disk resource. In the Node and File Share Majority model, a file share replaces the disk as a
disk-based vote. The Node and File Share Majority model is an excellent solution for
geographically dispersed multi-site clusters. In the Node and Disk Majority quorum model, the
disk resource is a shared disk, the witness disk.
Failover cluster administrators can select the quorum model of choice, depending on the
requirements of the clustered resource. The quorum model should be selected after the cluster
is first created and prior to putting the cluster into production.
Heartbeats
Heartbeats are network packets periodically broadcast by each node over the private cluster
network. Heartbeats inform other nodes of a single system's health, configuration, and network
connection status. When heartbeat messages are not received among the other nodes as expected,
the cluster service interprets this as node failure, and a failover begins.
Virtual Servers
Groups that contain an IP address resource and a network name resource (along with other
resources) are published to clients on the network under a unique server name. Because these
groups appear as individual servers to clients, they are called virtual servers. Users access
applications or services on a virtual server the same way they access applications or services on
a physical server. They do not need to know that they are connecting to a cluster and have no
knowledge of which node they are connected to.
Failover
Failover is the process of moving a group of resources from one node to another in the case of a
failure. For example, in a cluster where Microsoft Internet Information Server (IIS) is running on
node A and node A fails, IIS fails over to node B of the cluster.
Failback
Failback is the process of returning a resource or group of resources to the node on which it was
running before it failed over. For example, when node A comes back online, IIS can fail back
from node B to node A.
16 Introduction