Clustering vs Load Balancing vs High Availability

[Rajnish]

What is the precise difference between Clustering vs Load Balancing vs
High Availability? I have searched net but could not find satisfactory
answer. I want to know the answer in terms of application, servers and
system.

Suppose, I have an application APP1 (application) running on WebSphere
(server) on Windows OS (system). I want my APP1 to be available always
with better response time. Please answer in this context.

Thanks in advance.


-
Rajnish Kamboj

[Vikas Jindal]

Load Balance and High Availability is what you want to do and clustering is implementation of it.

Load Balance : My application is heavy i need to setup more than one server ,so that they can divide the load.

High Availability : My app is critical, it should be always up.

Clustering : Running of more than one server in such a way that they seem as one server to end user.


Difference between Load Balance and High Availability :

High Availability can be achieved in such a case,one server comes in to picture ,when other server goes done.This type of relationship can be called Failover.It is quite common in databases.

Load Balance can be achieved in such a case ,both server run parallely ,sharing each other load,but it may be possible that both may be down at same time.


Both of above cases of clustering.

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[Rajnish]

Thanks Vikas...
Further related queries:

#1 As per your comments in load balancing both servers can be down at
the same time, but the same could happen with two servers running in
HA mode?
#2 As per I have understood in HA mode only one server is active and
takes all the load and other server only comes into picture if primary
is down. Am I right?
#3 What happens to our transactions running on servers in load
balancing vs HA mode? Does the transaction run again in both?
#4 Can Load balancing be achieved between application running on same
machine and same server?
#4 Is it the separate server which control load balancing and HA
between different servers?
e.g. Suppose APP1 runs on Server1 (on machine1) and Server2 (on
machine2). Now Load balancing or HA runs on which machine?
#5 Can we achieve both Load balancing and HA mode simultaneously? If
yes what should be the ideal setup? Is the foll.right?

High Availability
/ \
Primary Node Secondary Node
| |
Load Balancing Load Balancing
/ \ / \
Server1 Server2 Server1 Server2


-
Rajnish Kamboj

On Sep 4, 6:37 am, Vikas Jindal <vikasjindal1...@gmail.com> wrote:
> Load Balance and High Availability is what you want to do and clustering is
> implementation of it.
>
> Load Balance : My application is heavy i need to setup more than one server
> ,so that they can divide the load.
>
> High Availability : My app is critical, it should be always up.
>
> Clustering : Running of more than one server in such a way that they seem as
> one server to end user.
>
> Difference between Load Balance and High Availability :
>
> High Availability can be achieved in such a case,one server comes in to
> picture ,when other server goes done.This type of relationship can be called
> Failover.It is quite common in databases.
>
> Load Balance can be achieved in such a case ,both server run parallely
> ,sharing each other load,but it may be possible that both may be down at
> same time.
>
> Both of above cases of clustering.
>

[Vikas Jindal]

Hi Rajnish,

First of all, Load balancing and High Availability are not totally separate concepts.There some thing similar
and something different.

#1 Yes,when both servers will be down in HA mode, app wont available. Thats why most of time ,one server is comes in to picture only when other server goes down.But again, app can be down in case of fail of both server. We always have concept of making thing difficult (less porbabelity of down of application ) , it is not possible to make in impossible.

#2 Yes, you are right.But HA can also be archived with a mix of Load Balancing ,with both server running.

#3 Not exact sure,but i think we can use concept of distributed transactions here.

#4 Yes, there is a separate server which do HA or Load Balacing. You might have heard of Mode JK in Tomcat,Cisco Load Balancer. It can run on any machine.

#5 Yes ,this is a good architecture.