Virtual Machine Software
Isn’t it ironic that Garrison Keillor’s show about fictional town Lake Woebegone is so popular and desirable compared to life in a real town, such as Los Angeles? There are more opportunities and functions in the real city, but the virtual city has all the star attractions. Similarly, virtual machine software has nearly eclipsed real-time operating systems, at least in terms of excitement. Why the buzz?
Virtual software permits you to run a number of copies of operating systems—even different operating systems, on the same system, usually irrespective of the base (or host) operating system. These guest operating systems run completely independently of each other, yet have virtual disks, NICs and other hardware.
On larger servers, with multiple processors, and more than 2 GB to 4 GB of RAM, you can consolidate multiple servers that were kept separate for reasons of security or other boundary considerations. Once you allocate resources to the virtual machine, that machine is independent of anything else installed on the host. I found all hosts and the virtual software to be stable, but I did find some speed penalty apparent when I ran benchmarks in the guests versus the host. This varied depending on what software I used for the virtual machine.
Even if most machines in your environment aren’t ready for migration to virtual machine software, VM still has many uses, especially for readers of this magazine. The best use of inexpensive workstation VM software is to run environments suitable for exam preparation. Both Novell and Microsoft now equip their traveling labs with one or two laptops per user, running VM software, emulating up to four machines.
Another great use of VMs is in testing or piloting programs. Most environments don’t have unlimited hardware, and the ability to prototype and run more complex scenarios is invaluable for checking interactions between directory-enabled software. More refined testing, where rapid, repetitive environments are needed, is also possible. The VM environment configuration is stored as a file, so that file can be copied and saved more easily than taking and restoring an image. I was able to take a server guest and run it on the workstation software merely by pointing to the saved file. Another enterprise use for simple VM software would be running legacy software on new hardware by supporting an older OS virtually.
The two most popular VM software solutions are Microsoft Virtual PC 2004 (www.microsoft.com/virtualpc) and VMWare’s (www.vmware.com) GSX Server and Workstation 4.5 (VM 4.5). I tried both products, using the same guest and host OSs. From a clean boot, with the same memory and disk configuration, I ran a number of synthetic benchmarks for Windows Server 2003. Since virtual mania is relatively new, Web sites that discuss how to set up your guest and host machines are plentiful, particularly for Linux. When testing or configuring NetWare, a helpful site can be found at www.robbastiaansen.nl.
Relative performance on host and guest across the VMs was consistent, and identical within the margin of error. Floating point and arithmetic computations were always highest on the host system, but otherwise slightly higher on the GSX server than VM 4.5, which was higher than VPC. With disk benchmarks, the highest performance again was also on the host.
Since Microsoft purchased the Connectix product, it has dropped support for other guest OSs, and though Linux and NetWare will run as guests, they are not directly supported. Both VMWare products have a large number of preconfigured OS virtual machines. Some features of Microsoft’s Virtual PC have changed: Formatted drive support was dropped, for example. USB devices and SCSI drives are not supported on the guest OS, and the product only uses one processor. VMWare’s default for GSX is to emulate SCSI drives. Otherwise, Microsoft’s Virtual PC is inexpensive and has a slick Undo disk feature that makes it possible to commit changes–or not–at the end of a session for each guest. Aside from measured speed differences, it was easy to switch from guest to different guest to host using Microsoft Virtual PC.
Whether you use Microsoft or VMWare, virtual technology is clearly the way to go for certification preparation. It mimics the new practicum from Novell and will give you practice at running software certain to be part of your enterprise, now or in the near future. Like Lake Woebegone, virtual life is sometimes easier to change than reality.
Douglas Mechaber, MCSE, MCNE, CCNA, BCSD, is always looking for software and tools to make his job easier at a large, government health organization. Send him your comments at firstname.lastname@example.org.