Load Balancing
14/08/2012
Load balancing within the IT field refers to a method of distributing workload across multiple computers, servers, network clusters, CPUs or other resources to best utilise all available resources.
There are many reasons for using load balancing, ranging from efficiency (utilising idle resources), minimizing response time (allowing huge programs to run faster) and to avoid unnecessary overload on one resource and provide a level of redundancy.
Some of the development team at Cornish WebServices were among the pioneers using load balancing or parallel processing to utilise underused resources on a network to speed up large and complex programs. Technology that was developed for the running of large engineering programs was then adapted and developed for providing website information to many people across the largest network (the Internet). Virtually all large internet sites, DNS servers now make use of load balancing to provide the high bandwidth and redundancy required.
Load balancing requires some extra software of hardware to act as a switch and direct the processing workload to one of a selection of processors or servers based on scheduling algorithms. These can be simple (random or sequential) or more intelligent (based on current load). A commonly quoted advantage of load balancing is the provision of redundancy on servers or databases. But just as key is the load balancer itself – and in many systems this presents a unique point of failure. If system redundancy is a reason for using load balancing then you must ensure you have redundancy on your load balancing switch.
Technically one of the trickier issues to get right with load balancing is the issue of ‘session persistence’ or ‘stickiness’. In a non https environment where data stored within cookies is limited using a load balancer with the requirement to remember visitor data will result in more work for the database. For some applications this will require additional database capacity. This is a reason not to use load balancing when not needed.
Large hosting providers can provide advice on setting up servers in a suitable configuration and can look after and maintain secure load balanced severs. If you invest money in load balancing then you should ensure your datacentre has redundancy on level 3 and tier 1 connectivity providers.
