A VPS, or virtual private server, is a method in which a server splits, thus appearing to act as multiple servers. Each server runs an individual operating system and individually rebooted. This practice is common in mainframe computers, and has grown more so now that virtualization software has become more developed.

The physical server usually hosts “guest” operating systems, and runs a hypervisor for each that is tasked with the creation, destruction and management of each virtual machine. Each guest operating system is given a share of the resources offered by the server. This guest system can be a virtual, paravirtual or any hybrid of the two.

When a guest operating system is virtualized, it is present with an emulated set of hardware, but is not aware of that the hardware isn’t physical. The hypervisor is in charge of translating and converting requests from the guest to the resources on the host. This creates massive overhead. Because it requires no modification of the operating system, almost any system can be virtualized, although a full CPU support virtualization is required for the hypervisor to perform fully.

The paravirtual environment is when the guest is aware of the hypervisor as it interfaces directly with the host’s system resources, while the hypervisor gains real-time access to the resource allocation. This is basically a near-native approach as the guest sees the exact same hardware as its host and communicates with it as such. An example of a system known to use paravirtualization is a UNIX-like system known as Linux.

Hybrids are really a full virtualization, but the guest uses paravirtualized drivers, including networking and Disk I/Os, which result in a massive increase in performance. When an operating system cannot be modified, it is usually supported by paravitualization.

Many up and coming companies are offering VPS hosting, or virtual dedicated server hosting as an extension for their web hosting services. Some hosts may reference the Virtual Private Server as a Virtual Dedicated Server/Dynamic Dedicated Server and vice versa. A few things to consider when licensing proprietary software in these multi-tenant environments are:
Unmanaged Hosting – This is when a customer is responsible for monitoring and administrating over their server.
Unmetered Hosting – This is like unmanaged hosting but with a fixed bitrate, which keeps you from exceeding your monthly budget.

The VPS can be run in a variety of ways, each running its own operating system, and bridging the gap between the shared web host services and the dedicated hosting services.