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Server Load Balancing

Posted On 2007-06-19 by FortyPoundHead
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Load balancing is the technique of spreading work between computers, hard disks, processes, etc. with the purpose of decreasing computing time and getting optimal resource utilization. This technique is generally performed by load balancers, whose aim is to exceed the capacity of a single server by increasing that of a server farm. Load balancers also allow the service to continue even in situations of server maintenance or server failure. Reducing downtime is essential in the prevention of huge losses, which is why automatic detection of server failure or server lock-up software are recommended.

But why is server load balancing necessary? If all the incoming HTTP requests for your website are responded to with only one web server, its capacity may fail in handling high volumes of traffic, when and if your website becomes popular. This means that pages will load slowly and there will be quite some time before some of the users get to have their requests processed by the web server. The more connections and incoming traffic to your website, the greater chances are you will need server upgrading, which may no longer be cost effective. This is what server load balancing is about: adding more servers and distributing load among them, in order to attain web server scalability. Be it an application server, database server, or HTTP server, load balancing applies for and is recommended for all types of servers.

There is a limit for each server as far as the number of users that it can server is concerned. Once that limit has been reached, you only have two options. You can either replace it with a newer one, or you can add one more server and make it possible that the load is shared between them. A load balancer will help you in that it will distribute connections among servers and cut the work proportionally for each of them.

Many server deployments can do with using basic information about the services and the clients they want to reach, as means for load balancing. Still, this will prove insufficient as your needs develop and become more complex. At this point, you have to take a closer look at the options you have and make a more detailed decision about load balancing. This is where Layer 7 load balancer comes into place.

There are times when sharing traffic over a group of servers simply is not enough. One reason is that all the content that comes with a request will have to be on each server, if they are equally likely to service that particular request. Your servers will function with maximum efficiency if you group them so as to handle different tasks at the same time. For instance, some can be optimized for streaming video downloading, others can serve as massive storage systems, while others can handle transactions. In fact, the main reason for using a load balancer is that of increasing the capacity of IP servers.

The ability to handle huge amounts of traffic is extremely important in a server load balancer. This is all the more true for sites with significant volumes of SSL transactions, which require built-in SSL terminations and SSL acceleration cards. Theses cards are very important to the security of transactions on e-commerce web sites through the encryption keys that they generate. But the process of performing a secure transaction can overload a server severely, which results in a smaller number of transactions being processed by second. This ultimately leads to fewer sales. The importance of SSL acceleration cards is obvious, as they take over the process, subsequently allowing the load on the server to be reduced. Under these circumstances, the Layer 7 load balancer can perform correctly, despite the large number of HTTPS packets coming in. The ideal product will increase efficiency and reduce costs, as it provides performance and quality, and requires no separate appliance.

Layer-7 load balancer is concerned with parsing requests and distributing them to servers, according to the different types of content these requests have. By doing so, Layer-7 load balancer improves overall cluster performance, although its scalability is rather limited compared to Layer-4 load balancer, due to the high overhead of parsing requests.

An important feature of any efficient Layer- 7 load balancer is its ability to manage traffic based on the content. Traffic management is performed by comparing URL content with customized configuration settings. This process helps to determine which server is able to handle the request and making an appropriate routing.


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