Virtual Private Server (VPS) technology has become quite a popular alternative to more traditional shared hosting, as it offers far greater flexibility for little extra cost. Unfortunately, it is a way much easier to choose between shared hosts than to pick the virtualization technique that would suit you best. If you’re planning to use VPS technology but don’t know the choices, I’ll present you with a few popular virtualization technologies.

Generally, there are two major categories of virtualization, both having advantages as well as disadvantages. The simplest type is at the operating system level. When a new server is supplied, it comes with its own virtual space owing to a fresh OS install made in a subdirectory on the hosting system. The server and its processes are still visible to the main operating system, though they are separated from any other virtual installations such that one server’s users and processes cannot interfere with those of any others.

This particular kind of operating system virtualization has several major advantages. First, it generally requires fewer resources than are needed by other virtualization mechanisms, and as such is less expensive to administer. Servers of this sort can also generally be administered more easily and reliably, as they rely on the host’s kernel and are generally not prone to lockups introduced by using custom kernels with other virtualization solutions.

Still, there are also disadvantages. With operating system virtualization you are bound to use exclusively the kernel installed on the OS host - no different version or separate one are an option. One consequence of this is that OS upgrades to take advantage of new technologies may not be possible with OS-level virtualization, as it is necessary to justify upgrading all servers on a given host simply to upgrade one. It is also difficult to thoroughly isolate and control resource use such that one user’s server does not consume more than their allotted share.

Another virtualization technology involves emulating the underlying hardware on which an operating system runs, then installing it atop this virtual computer. Since virtual servers are for all purposes independent of the host’s hardware, they may support various kernel versions, or even completely different OSs.

This is one of full virtualization’s greatest advantages. Rarely is a computing environment homogeneous enough to justify a single OS version on every single server, especially in hosting situations where flexibility is a key selling point. Furthermore, most full virtualization solutions allow for the installation of custom kernels, making it possible to use VPS technology with new device drivers and kernel level technologies not anticipated by the provider.

Of course, these advantages come at a cost. Full virtualization generally requires more system resources and therefore is more expensive to host. The ability to install custom kernels and operating systems introduces additional administrative overhead which, in the wrong hands, can render full virtual machines much less stable than are their OS-level counterparts.

Virtualization technology has begun to completely revolutionize our concept of web and other forms of hosting. The choice is not confined to the limited shared hosting and expensive dedicated servers anymore. To benefit from from the emergence of new hosting alternatives, it is crucial to understand the virtualization landscape and know all available options.