Cluster

[Vishakha Ahuja]

Hi,
How does clustering of web servers affect scalability, maitainability, availability and performance of an enterprise application ?
Also, how does clustering of application servers affect all the above ?
Thanks in advance,
Regards,
Vishakha.

[Deepak Shah]

check out my latest post on Load balancing web application.
Hope it addresses your concern !
Thanks,

[Rahul Mahindrakar]

Ahuja
clustering of web servers affect
scalability : Horizontal Scalability/Load Balancing is acheived through Clustering so more machines in cluster more is the scalability.
maitainability ; the more the machines in a cluster the more difficult it is to maintain the application
availability : Things like failover management in clustering help increase availability
performance : hmm.. I am doubtful about this.

[herve attia]

One of the best approach to improve performance, scalability and maitainability of your distributed system is the clustering.
You distribute load among a set of distributed servers using load balancing mechanism.
Data replication and data caching increases the performance as well.
But nothing is free is these world...you need to add some strategies to preserve a consistency system.
If your application needs a strong consistency system (active replication strategy), these strategy might impact the availability,latency of your system because for each request receives by your system, each replica has to process the request in a determinist approach (give the same result)....before to senb back to response to the client...
So I invite you to read articles about load balancing, replication (active, passive, semi-passive), fault tolerance....
herve attia

[Vishakha Ahuja]

Thank you all.
So, I understand clustering of web servers improves scalability and availability.
Does this mean that clustering of Application Servers (EJB servers) also improves Scalability and Availability ???
And what happens to reliability ?

[SJ Adnams]

yes, yes & yes.
You will have more CPU's which means more jvms.
You have hardware redundancy.
In iPlanet the session can be configured to reside in the kxs or kjs engines so that increases reliabilty?

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[Jim Yingst]

I'm transferring this to our new iPlanet forum...