Wednesday, August 7, 2013

What is Load Balancing? How Load balancing helps in improved performance?

Load balancing is mainly to distribute the workload across multiple computers or a computer cluster, CPUs, disk drives, or other system resources.

This optimizes resource use, maximizes throughput, minimizes response time, and avoids overload. Using multiple components with load balancing instead of a single component may increase reliability through redundancy. Load balancing is usually provided by dedicated software or hardware, such as a multilayer switch or a Domain Name System server Process.

Why to do Load Balancing?
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From the first glance it looks like an overhead but it is not; actually this helps us to improve performance.

1.      Load balancing increases scalability to accommodate higher volume work by distributing (balancing) client requests among several servers. This allows more servers (hosts) to be added to handle additional load.

2.      Load balancing ensures uninterrupted continuous availability of critical and key business applications. When the applications are on more than one machine, operations personnel can work on one machine while the other is busy working.

3.    It helps the system to be ready to accept and handle growth and make it fault resilience, so if a server crashes or just needs maintenance work done, an alternative server can take over.


There are various algorithms for load balancing and it totally depends on the context which one you want to use. Some of them are listed below:

1.    Round robin: This distributes the request to different servers in a round robin manner independent of the load on each server. The problem with this type is it works blindly and even if server is overloaded it will queue the request.

2.    Denoted Connections: This algorithm keeps track of the number of active connections to each server and always sends new request to server with least number of connections. If two servers have same number of connections, it selects the server with lowest server identifier. The disadvantage with this is when system is empty the same server is used all the time.

3.    Round Trip: This algorithm monitors the first buffer time for each connections of the servers. The mean time is calculated over a averaging window and the average value is reset at the end of averaging window. The server with least mean value will get the request. This is complex and can be implemented with limited set of variables.

4.    Transmit Byte: This algorithm keeps track of the amount of transmitted bytes from each web server since the last averaging reset and uses this to allocate the request to the server.

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