What is Load-balancing and Do I Need It? - Software Load-balancing
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What is Software Load-balancing?
Many web servers, including the popular Apache Web Server, have built-in support for load-balancing. While using a software configuration to accommodate your load-balancing needs is a less expensive approach than a hardware-centric approach, it tends to be much less robust, and suitable mostly for medium-to-low traffic scenarios.
The most popular software load-balancing solution is called ‘DNS Round Robin’. Simply put, DNS Round Robin sits on a server in front of your web servers, and as requests come in for web pages, it hands them to the next available web server to be processed. In this process, each server is hit sequentially, in turn. So, if you have three boxes on a DNS Round Robin configuration, the sequence of page requests would be server1, sever2, server3, server1, server2… I’m sure you get the picture. Unfortunately, this method of load-balancing does have some limitations:
- There is no way of telling that a skipped server is down or is just busy.
- The type of data requested is not taken into consideration. Images and other supporting files may benefit from sitting on a different server than the ones processing scripting and database logic.
- The server containing DNS Round Robin is a single point of failure. If for some reason this server becomes unavailable, your other servers will never receive any traffic.
- As your site grows and more servers begin to be implemented, this solution becomes more difficult to configure and manage.
There are a number of software load-balancing solutions on the market, but most tend to be geared more to smaller sites and simple networks. The software solutions that can handle the more robust requirements often require a sizable investment in hardware for them to handle the traffic adequately.
Next: Hardware Load-balancing >>
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