difference between clustering and loadbalance

[Sanju]

Hi,
what is the difference between Loadbalance and Clustering.
Mohan

[Malli Raman]

Originally posted by sunita mohan:
Hi,
what is the difference between Loadbalance and Clustering.
Mohan

Clustering is used for Load balancing the server.

[Paul Sturrock]

Clustering is used for Load balancing the server.

No its not.

Clustering is the practice by which multiple instances of an applciation servers running in multiple VMs are configured to behave (from the end user's point of view) as if they were one server instance. To that end Clustering requires redundant information - such as the Session - be maintained accross all clustered instances. If one server goes down the user's requests are transparently transfered to another.

Load balancing is just the technique whereby users' requests to a single application are redirected to one of a number of redundant servers depending on load. These servers may or may not be clustered - indeed they couild be entirely independent of each other. Clustering uses load balancing to decide which if its available server instaces handles the request. Unlike clustering though load balancing doesn't necessarily imply that the transfer will be transparent.

[ December 16, 2004: Message edited by: Paul Sturrock ]
[ December 16, 2004: Message edited by: Paul Sturrock ]

[Ajai]

Hi Paul,

I too feel quite confused by these two terms and another term failover.

From above can I say that failover is just a concept which is realized by both clustering and load balancing.

One more question regarding the diff between clustering and load balancing is.
Is the software used for deciding which server to choose both in case of clutering/load balancing not the same?

Thanks,
Ajai

[Malli Raman]

Originally posted by Ajai Sandhu:
Hi Paul,

I too feel quite confused by these two terms and another term failover.

From above can I say that failover is just a concept which is realized by both clustering and load balancing.

One more question regarding the diff between clustering and load balancing is.
Is the software used for deciding which server to choose both in case of clutering/load balancing not the same?

Thanks,
Ajai

Can I say load balancing is used for control the clients request traffics?
Load balancing controller will redirect client request to a particular app server /web server either as round robinwise or a particular client is tied up with a particular webserver/app server.

Fail over mechanism is different from Load balancing. Fail over server will have same kind of web/app server setup available in production environment. When the main server goes down the auxilary server will start automatically(I am not sure!).

I am not sure load balancing can be used for fail over mechanism. Because I have observed that in cisco based router load balancing won't support the fail over.