Load balancing enhances and expands a Web site’s capacity to deliver in-demand content.Load balancing enhances and expands a Web site’s capacity to deliver in-demand content.
Load balancing hardware and software allows Web site traffic to be shared by two or more servers. Serving up your site through multiple pieces of software and equipment allows you to ensure faster distribution of your content when your site becomes saturated with requests. Load balancing allows the server and network infrastructure of popular Web sites to respond to huge influxes of users more effectively.
The managers of extremely popular Web sites thus seek load balancing as an integral feature of their hosting requirements. Established and accomplished hosting firms are therefore proud to offer load balancing as a major building block of their advanced hosting solutions. But simply because a host offers load balancing functionality, it does not mean that it is a solid solution.
Load balancing initially emerged as a creature of network administration creativity. Systems administrators trained in domain name maintenance deployed “round-robin” DNS systems to rotate traffic to two servers.
With the BIND name server, version 4.\’ or greater, a specific Web address can be assigned to two or more IP addresses, thus allowing users to seamlessly access one Web site distributed amongst two or more physical servers. This is permitted because the name server alternatively rotates IP addresses for any server request. In most cases, with two Web servers, each server handles 50% of traffic. This method of load balancing had great merit, but encapsulated one fatal flaw. If one server crashed, 50% of all users requests would go unanswered.
More importantly, the DNS system has no mechanism to verify whether a Web server is online and functioning properly. This means that if your system failed, you would have to manually verify the outage. For these reasons, you mustn’t blindly sign on with a host simply because they offer a load balancing solution. It is the onus of the sophisticated hosting client to determine whether the load-balanced solution is sound.
“This means that if your system failed, you would have to manually verify the outage.”
A sound solution will use a multi-node “cluster” architecture that provides high availability and scalability. Such an architecture distributes the load so that if one of the hosts in the sever facility were to fail, the load will be distributed among the remaining hosts without any service interruption. This architecture is called “clustering,” and is more reliable than the DNS round-robin option because of the design of its topology.
Clustering topologies employ a ‘heartbeat mechanism’ within each server to monitor sever health. The primary server sends periodic messages to the alternate server to determine whether the server is functioning properly. If the flow of messages is impeded for any reason, then the viable server assumes that the other server has experienced a fatal failure and puts itself into operation in place of the failed server. This intelligent mode of server distribution is the preferred method of cluster-based load balancing, and assumes two forms: passive and active.
A passive load balance arrangement is when one server acts as a primary server, with a secondary server only available for use should a failure occur in the primary server. With the passive approach, a secondary server is never used for any other processing except in the event of a failure. Conversely, the active load balance approach distributes all incoming request amongst both the primary and secondary server in the cluster. Usually it is more cost-effective and efficient to use the active method in order to improve the performance of a busy site.
But no matter what method of load balancing you select, ensure that it is a cluster-based model so that your heavy trafficked Web server and e-commerce traffic is protected from outages caused by too many user requests. Sophisticated load balancing systems are available from only the best hosting firms.
As you can see, a proper and robust load balancing system will increase the performance and reliability of your high traffic website – and when dollars are on the line, the effort is well worth it…
