Basic High-Availability Cluster Concepts for beginners

Basic High Availability Cluster Concepts, cluster concepts, cluster tutorials, linux cluster basics, cluster basic tutorial, tutorial linux cluster

Basic High-Availability Cluster Concepts for beginners

I have made this tutorial only for the beginners to know the basic purpose of high availability cluster and concepts clearly.

What is availability & high-availability?

Availability can be measured relative to "100% operational" or "never failing.". yes of course, we wanted our configured services in a server to be available continuously without any downtime.

Here i refer configured services as that might be your file based shares (nfs, samba services) or web services, application services or databases. could be anything.

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So What and all we can do to have our server to be available continuously?

1. Buying a server with redundant power supply - so if one power supply fails, server will be still available with one power supply.
2. Configuring a hardware raid and installing our OS - so if one disk fails, raid will make our OS to be running from other operational disk.
3. having multiple network cards configured teaming or bonding with single ip , here also if one link goes down, client users will be still able to access the server from other available network links.


Fine, we have done something for availability as the images shows.

Do you think our server will be 100% operational and available without any issue. ?

what about our OS if it gets hung or kernel panic? because our OS doesn't have redundant?

Here only Actual high-availability comes into picture.

Definition of High-Availability cluster is,

A high availability cluster (HA cluster) is a group of computer hardware pieces that provide solutions for redundant operations, in the event of component failure.

I would say high-availability mostly for your operating system. commonly used cluster is two node cluster, but we can have up-to 64 node cluster.

Two types of clusters;

1. Manual cluster - which is nothing but you will have some downtime to bring up the other node with same data and ip address. End users still able to access the nfs shares but they dont from which server they are accessing. This is manual cluster.

2. Automatic Cluster - here we use some sort of cluster software's such as veritas cluster, HP Service-guard cluster, Red Hat Linux Native cluster, Sun Cluster, IBM AIX based Clusters.

These software's will do the necessary switchover automatically which is already configured by us in the respective configurations.


We will see some of software based automatic clusters like how to install, configuration, what and all required in upcoming tutorials. Hope this helps someone, please share and subscribe free for more.
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June 11, 2015

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