The Domain Name System is an Internet naming system that makes it possible to assign domain names to groups of Internet resources and users, independent of each entity’s physical location. Domain names are easier to remember than IP addresses such as 207.75.188.166 (IPv4) or 2001:db6:1f70::999:de8:7648:6e8 (IPv6). Internet users use domain names to recite meaningful Uniform Resource Locators (URLs) and e-mail addresses.

The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating name servers for each domain. Name servers are responsible for their particular domains. The are DNS distributed and fault tolerant. This makes possible for the WWW to avoid keeping everything in a single central register which has to be continually consulted and updated.

Domain Name System also stores information about the list of mail servers that accept email for web addresses. Domain Name System is a very important component of the Internet as we know it because it provides a distributed keyword-based redirection service.

“VPS” is an abbreviation of Virtual Private Servers. This is a type of web hosting service achieved though dividing a physical server into a number of virtual instances. This is possible thought different virtualization techniques.

Virtual Private Server (VPS or VPS Hosting) is a broadly used term which refers to a virtual machine (VM). The virtual machines or VPS are functionally equivalent to a any physical server (dedicated server). Another term – Virtual Dedicated Server (VDS) – also refers to a virtual instance, however it is usually used to explain a virtual server result of different concept of virtualization – Full virtualization.

Any physical dedicated server runs a hypervisor which creates, destroys, and manages the resources of “guest” operating systems or virtual machines. The guest OS are allocated a percentage of resources of the physical machine. The Guest system or VPS may be fully virtualized, paravirtualized, or a hybrid of these two.

In a fully virtualized server, the guest represents an emulated or virtualized set of hardware. It is unaware that this hardware is not strictly physical. The hypervisor translates, maps, and converts requests from the VPS into the appropriate resource requests on the host, resulting in significant overhead.

In a paravirtualized (Paravirtualization) server, the VPS is aware of the hypervisor and interfaces directly with the underlying physical server’s resources. In this virtualization technique the hypervisor implements real-time access control and resource allocation. This results in near-native performance since the VPS sees the same hardware as the physical machine and can thus communicate with it natively. Linux OS supports this method of virtualization.

Advantages of Virtual Private Servers

• Owners and server administrators have full root access to the virtual machine
• Any VPS account is isolated from others accounts on the same physical server
• The VPS owner does not need to deal with hardware or to deal with any replacements or physical upgrades, because the web hosting provider is responsible for the management of the underlying physical server
• From user’s perspective the VPS are easy to be scaled up and down and used on a per demand basis
• A VPS is cheaper than a physical server with similar amount of resources

Disadvantages of Virtual Private Servers

• Compared to any form of Virtual Hosting (Shared Hosting) the VPS are hard to manage, because they require someone to do a system administration and maintenance, OS and applications’ installation, etc.
• Unlike physical dedicated servers, the CPU, RAM, HDD space, disk I/O and other computing resources are still shared between different users of the same underlying physical server. However in some forms of virtualization like Full virtualization, we can not say that the resources are shared.