Underneath all the "virtual" in Microsoft Virtual Server (MVS) 2005, there's a layer of very real hardware, including storage. If you haven't provided adequate storage capacity, your virtual systems can come to a virtual standstill.
MVS 2005 lets an enterprise run multiple copies of different operating systems on multiple virtual machines, which offers major advantages in performance and security.
However, to keep MVS 2005 from turning your operating systems into underperforming slugs, you must give it the resources to breathe. That means you need enough disk space for the underlying operating system -- Windows Server 2003 -- and copies of each guest operating system you will be running.
At a minimum -- a bare minimum -- allow 4 GB of disk space for Windows Small Business Server (standard or premium edition) and 2 GB each for Windows Server 2003 (standard, enterprise or datacenter edition). You also have to add space for the paging file and overhead for the virtual machines. As a practical matter, that usually doubles the disk requirements.
In addition, you need enough space for each of the guest operating systems, plus at least 32 MB for overhead for each copy of a guest operating system.
Don't be stingy. Next to RAM, disk space has the greatest effect on the performance of Virtual Server 2005. Besides disk capacity, you want disk speed. Fast hard disks pay big dividends in virtual machine environments, and that's as true for Windows Virtual Server as
IBM discusses this and other issues relating to Virtual Server 2005 in its Redbook titled, "Introducing Microsoft Virtual Server 2005 on IBM eServer X-Series Servers." It is available at: http://www.redbooks.ibm.com/redpieces/pdfs/redp3912.pdf.
Although the discussion is aimed at IBM's servers, much of the information is useful to anyone deploying Microsoft Virtual Server 2005.
Rick Cook has been writing about mass storage since the days when the term meant an 80 K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last 20 years he has been a freelance writer specializing in storage and other computer issues.
This was first published in May 2005