Technology Trends: Server Virtualization Home

A number of SYS-ED clients have been evaluating and implementing virtual servers. Given the evolution of hardware, operational challenges in information technology, and the underlying economics, there are compelling reasons to expect this trend in server virtualization to continue. With 30+ years in data processing and first generation experience in internetworking, server virtualization is many ways a redux of VM on mainframe systems, albeit in the form of virtualization software for Microsoft networks and UNIX variants.

Virtual servers provide the capability for creating an internal network; which is a network servicing only the virtual machines. This allows the virtual machines to communicate with one another through a dedicated backbone without having to place packets on the physical network. Virtual servers work just like physical servers when it comes to sending and receiving traffic on the network and purposely applied will have no impact on the network. However, network performance can suffer if multiple virtual servers share the same physical network adapter. In such cases, the network adapter may cause a bottleneck for the virtual servers. Accordingly, sound planning will call for installing multiple network adapters and setting up the virtual environment in order that each virtual machine gets its own network adapter.

Internal networks are accessible only to virtual machines. Virtual machines, their operating system, and everything else that they contain all exist within a single virtual hard drive file. As with any file, a virtual hard drive file is simple to move from one machine to another. Virtual server software has mechanisms in place to prevent a single virtual server from consuming all of the physical server's resources, this will prevent a single virtual server stealing memory from another. When a virtual machine does not have sufficient resources to run the application, there are choices in configuration choices which can be selected. One option is to reallocate the physical server's resources. Another option is to move the virtual machine to another physical server that is not being as heavily utilized.

Virtual machines are self-contained environments. If a virtual operating system produces a blue-screen error, the crash affects only that virtual machine. The host operating system and any other virtual machines that may be running are all isolated from the crash. However, virtual machines are dependent on the host operating system. If the host operating system crashes, every virtual machine on the server will also fail.

Another reason for implementing virtual servers is to help reduce the administrative burden. One way the administrative burden is reduced is that the backup process is greatly simplified when virtual servers are used. Virtual servers make use of a virtual hard drive, which is a file residing on the host machine. This affords the capability to back up the virtual machine in less time and with less effort than is usually involved in backing up a physical server.

In SYS-ED internetworking courses we offer clients the option of having us provide the training with virtualized servers.