Server Virtualization

Server virtualization is a part of IT virtualization.

Creating a virtual environment

Many system administrators choose to set up multiple servers. This is for a reason: it is recommended to devote different servers to different tasks. For example, Microsoft urgently advises to never run both Active Directory domain controller and Internet gateway on the same physical server, since it introduces a security threat. In case of malware or hacker attack on the network, Internet gateway is first to take the brunt. And if the domain controller shares the server under attack, AD bases will probably get corrupted or even worse – leaked to hackers. While outcome of corruption is just spending some time on recovery, in case leak happens more elaborate attacks are very likely to come using logins and passwords of actual network users. The least bad thing that can happen is that all company users’ e-mail addresses make their way to spammer bases.


With respect to the above, domain controller is installed to one physical server and Internet gateway is installed to another. This is correct. Now if hackers deploy a successful attack on Internet gateway, chances that they will reach anything past the gateway will be much lower.


Every separate server has its cost. If we’re speaking about brand servers here, the costs fly up. Each server consumes electric power, occupies place on a table or a stand. Besides, server applications rarely consume large portion of system resources: CPU load doesn’t exceed 10% for domain controllers and Internet gateways that we mentioned. Thus using a separate server for each of these tasks is seen as irrational. On the other hand, using a single server is unacceptable in terms of security. Well, where is the happy medium then? The answer is given with server virtualization .


What is server virtualization?


Server Virtualization is a software technology of computer’s hardware emulation. One physical computer can run multiple virtual machines at once. Such virtual machines act just like separate physical ones; you can install operating systems and applications to them. Each virtual machine uses a portion of physical host’s resources for its operation. And the portion of resources reserved for use can be adjusted either statically or dynamically. This technology allows a more rational usage of hardware resources.
Example: we have two applications that require 128 Mb RAM each and cannot be installed to the same physical server.

Our options are:


  1. Buy two servers having 256M RAM each;
  2. Buy one server having 512M RAM and run both applications within separate virtual machines;

Obviously, the latter option makes for more effective hardware resources usage (CPU in particular), while the cost of server virtualization is much lower, since one server having a larger RAM capacity is always cheaper than two servers. See all server virtualization benefits.