Tuesday, August 12, 2014

Clustering

Clusters Configuration

Cluster Configuration can be done in two ways or two types:

1. Active/Active: Active/Active is Cluster type in which both Servers are working.

2. Active/Passive: Active/Passive is Cluster type in which One Server is working and other Server is   in idle condition.


What is Cluster?

A Server Cluster is a group of computers or servers running Windows Server 2003 or Server 2008 Enterprise or Data Center Edition and working together as a single system to provide high availability of services for clients.

When a Failure occurs in one Server in a Cluster, resources are redirected and work load is redistributed to other servers in a cluster.


Microsoft Server Cluster can support against three types of failures:

1. Application and Service Failure

2. System and Hardware Failure

3. Site Failure in multisite organization.


Dependencies: 

Microsoft Server Clusters use IP base protocol and Depends on Following:

1.  Active Directory

2. DNS 

Note: Cluster Service does not support use of IP adress assign from DHCP Server. 


Failover: 

It is the process having Cluster resources migrate from an unavailable node to available node.

Failback: 

When resources are restored to the node that has been offline after it is back online.


Failover is a automatically initiated by Cluster service when it detects the failure on one of the Cluster Node,because each Cluster node monitors its own process and the other node monitor its own process so that need for failover is detected without any delay. 




Types of Cluster:

1. Single Quorum device or Standard Quorum Cluster: This is most widely use Cluster type. In this type of Cluster their can be multiple nodes with one or more Cluster disk array also called the Cluster Storage and a Connection device that is bus.

Each Disk in the array is owned and managed by only one server at a time. It also contains the Quorum resources.

2. Majority Cluster Nodes sets: In Majority nodes set Cluster, each node maintains its own copy of cluster configuration data. The Quorum resource keeps configuration data consistence across the, node. For this reason this Cluster can be used for geographical dispersed location. Another advantage of Majority Cluster node set is that a Quorum Disk can be taken offline for maintenance purpose and the Cluster will continue to operate.  


  • The Difference between Majority Node set Cluster and SIngle Quorum device Cluster is tha Single Quorum device Cluster can operate with just one Node but Majority Node set Cluster need to have a majority of the Clusters node available for the Cluster to operate.