Clustering is a technology, which is used to provide High
Availability for mission critical applications. We can configure cluster by
installing MCS (Microsoft cluster service) component from Add remove programs,
which can only available in Enterprise Edition and Data center edition.
In
Windows we can configure two types of clusters
NLB
(network load balancing) cluster for
balancing load between servers. This cluster will not provide any high
availability. Usually preferable at edge servers like web or proxy.
Server
Cluster: This provides High availability by
configuring active-active or active-passive cluster. In 2 node active-passive
cluster one node will be active and one node will be stand by. When active
server fails the application will FAILOVER to stand by server automatically.
When the original server backs we need to FAILBACK the application
Quorum: A shared storage need to provide for all servers which keeps
information about clustered application and session state and is useful in
FAILOVER situation. This is very important if Quorum disk fails entire cluster
will fails
Heartbeat: Heartbeat is a private connectivity between the servers in the
cluster, which is used to identify the status of other servers in cluster.