In my previous post, I’ve just touch Red Hat High Availability Add-on for Red Hat Enterprise Linux and it’s eliminate single point of failures, so in case if the active cluster member on which a high availability service group is running become inoperative, the high availability service will start up again(fail over) in another cluster node without interruption.

Okay let’s get started with high availability clustering! but first of all, let’s understand some basic concepts. if you need clear and fully understand about all of these things, I highly recommend to read Red Hat Enterprise Linux 6 Cluster Administration Guide. It’s the best resources for RHEL6 HA clustering. and also you can use CentOS or Oracle Linux as alternatives to follow this article series without Using Red Hat Enterprise Linux.

##Cluster Node

Cluster node is a server that is configured to be a cluster member. Normally shared storage (SAN,NAS) is available to all cluster members.

##Cluster Resources

Cluster resources is the things you going to keep high available and all of these resources need to available for all cluster nodes. all or some of these resources can be associated with an application you plan to keep highly available.

##Cluster Service Group

A collection of related cluster resources that defines actions to be taken during a fail-over operation of the access point of resilient resources. These resilient resources include applications, data, and devices.


Fencing is the method that cuts off access to a cluster resource (shared storage, etc.) from a node in your cluster if it loses contact with the rest of the nodes in the cluster.

There are some more things related to clustering including this basic components and we can learn most of them when we deploying our high availability web service. So wait till the next post 😉