Large data demands, most commonly the result of multimedia storage and streaming, and simple expansion have demanded that more spacious, more scalable web hosting options become available. Simply building bigger servers is the typical solution, but growth has a way of outpacing technological capabilities.
The theoretical reverse of shared servers is to enlist multiple servers under a single entity. This may take various forms, with the simplest being a redundant or backup server that mirrors your main server to minimize downtime or to take the load off of a busy server. If the data is properly mirrored and synchronized, your gains in speed and reliability can be enormous. However, you are essentially still using one server (while paying for two!).
Clustered servers, on the other hand, may spread the total data across multiple machines. When done correctly, you achieve the speed and reliability of redundancy while also granting yourself extra space (and when done incorrectly, you vastly multiply the possibility for downtime, security holes, and missing data). ‘Load balancing’ is the key to stabilizing the multiple servers, and combining this option with redundant mirrors you can create a truly robust and stable entity.
At the extreme end, and also at the forefront of current focused trends, is cloud computing. Cloud hosting is the web hosting side of this theory, which spreads the hosted entity across numerous servers in much the same way as with a clustered server…except that cloud hosting may be spread across multiple servers that are not completely dedicated to a single entity. In a way, this hearkens down the scale to virtual private servers — except that no self-contained server exists on a single partition of a server in a cloud system (in fact, there are no ‘partitions’, and there may or may not be any distinct ‘servers’!).
The most significant element of the evolution of web hosting towards cloud servers may be the ‘metered’ nature, the utility model in which the user pays only for resources used (rather than the entire server, all the time). In practice, cloud hosting has been comparatively more expensive…but the utility model may change that, in addition to being (as proponents claim) “infinitely scalable”.