Virtual private server
A VPS runs its own copy of an operating system (OS), and customers may have superuser-level access to that operating system instance, so they can install almost any software that runs on that OS. For many purposes they are functionally equivalent to a dedicated physical server, and being software-defined, are able to be much more easily created and configured. It is this configuration of the VPS that allows affordability with performance, but that can come at a cost. They are priced much lower than an equivalent physical server. However, as they share the underlying physical hardware with other VPSes, performance may be lower, depending on the workload of any other executing virtual machines. More often than not during peak hours, performance of the VPS can drastically reduce slowing things right down.
The force driving server virtualization is similar to that which led to the development of time-sharing and multiprogramming in the past. Although the resources are still shared, as under the time-sharing model, virtualization provides a higher level of security, dependent on the type of virtualization used, as the individual virtual servers are mostly isolated from each other and may run their own full-fledged operating system which can be independently rebooted as a virtual instance. Virtual instances can benefit the customer in many ways as they are not using a physical machine. Independent rebooting of a VPS give customers flexibility and performance to manage their own system, such as independent partitioning.
Partitioning a single server to appear as multiple servers has been increasingly common on microcomputers since the launch of VMware ESX Server in 2001. The physical server typically runs a hypervisor which is tasked with creating, releasing, and managing the resources of “guest” operating systems, or virtual machines. These guest operating systems are allocated a share of resources of the physical server, typically in a manner in which the guest is not aware of any other physical resources save for those allocated to it by the hypervisor. As a VPS runs its own copy of its operating system, customers have superuser-level access to that operating system instance, and can install almost any software that runs on the OS; however, due to the number of virtualization clients typically running on a single machine, a VPS generally has limited processor time, RAM, and disk space. Limited process time and disk space of a VPS usually means a poorer performance.
Ultimately, it is used to decrease hardware costs by condensing a failover cluster to a single machine. Precisely the reasons for implementing VPS and thus decreasing costs dramatically while providing the same services. It is exactly this that makes a VPS affordable for most customers. Server roles and features are generally designed to operate in isolation. For example, Windows Server 2019 requires a certificate authority and a domain controller to exist on independent servers with independent instances of Windows Server. This is because additional roles and features adds areas of potential failure as well as adding visible security risks (placing a certificate authority on a domain controller poses the potential for root access to the root certificate). This directly motivates demand for virtual private servers in order to retain conflicting server roles and features on a single hosting machine. Also, the advent of virtual machine encrypted networks decreases pass-through risks that might have otherwise discouraged VPS usage as a legitimate hosting server. This is great for the customers of the servers.
Many companies offer virtual private server hosting or virtual dedicated server hosting as an extension for web hosting services. There are several challenges to consider when licensing proprietary software in multi-tenant virtual environments. As such a VPS may be used to reduce cost, but these proprietary softwares can add a knock on effect to cost.
With unmanaged or self-managed hosting, the customer is left to administer their own server instance. Though this can be challenging for non VPS gurus, those who have some software knowledge can do this easily.
Unmetered hosting is generally offered with no limit on the amount of data-transferred on a fixed bandwidth line. Usually, unmetered hosting is offered with 10 Mbit/s, 100 Mbit/s or 1000 Mbit/s (with some as high as 10Gbit/s). This means that the customer is theoretically able to use ~3 TB on 10 Mbit/s or up to ~300 TB on a 1000 Mbit/s line per month, although in practice the values will be significantly less. In a virtual private server, this will be shared bandwidth and a fair usage policy should be involved. Unlimited hosting is also commonly marketed but generally limited by acceptable usage policies and terms of service. Offers of unlimited disk space and bandwidth are always false due to cost, carrier capacities and technological boundaries. This is one limitation that a VPS has that the provider will never tell the customer. So always make sure you get a second opinion or better yet contacting someone you know with VPS experience.