Virtual Server 2005 R2 gives network administrators an easy way of consolidating multiple servers and operating systems on to a single computer. Instead of using a dedicated server for every application and service you require, you can run them on virtual server instances. This lets you continue to isolate applications and services while making better use of your existing hardware.

Virtual Server 2005 R2 supports up to 64 virtual machines on a single host. In reality though, the number of virtual machines you can successfully run on a single host will depend on the physical hardware - specifically the amount of RAM and available hard drive space.

In this series of articles, I’ll talk about some of the things you need to consider when deploying multiple virtual machines on a single server using Virtual Server 2005 R2. I’ll also discuss any requirements that are unique to this situation.

System Requirements
The number of virtual machines you plan to run simultaneously on a host will have an impact on the host computer’s system requirements - specifically on the amount of memory and hard drive space required.

Memory
Memory is critical when running multiple virtual machines on a single host. The minimum requirement to install Virtual Server 2005 R2 is between 256 and 512 MB, depending on the host platform you are running. These values however are just starting points. If you plan to run more than one guest operating system simultaneously, you need to increase the RAM. A general guideline to follow is to add an additional 32 MB of RAM for each virtual machine.

Note: When calculating the amount of RAM, don’t forget to factor in the RAM required to run host operating system.

Disk Space
Adequate disk space is just as important as adequate RAM since each virtual machine will have its own page file and dynamically expanding virtual hard disk. Additional space may be required, on top of this, if you plan to put your virtual machines into saved states. Virtual Server 2005 R2 requires a minimum of two GB free disk space. This amount will therefore need to be adequately increased for each virtual machine you plan to install.

Note: Multiple processors can improve the performance of the host operating system and Virtual Server 2005. However, guest operating systems themselves cannot take advantage of multiple processors.

Tags: virtual machine, networking