Understanding the difference between Microsoft Virtual
Server 2005 and Virtual PC 2004
December 9, 2004
Scott Lowe MCSE
Deploying virtual machines in your organization can save you hardware
costs and administration headaches, but what do you choose for software?
Microsoft itself offers two virtual machine software programs. Here are the
differences between Virtual Server 2005 and Virtual PC 2004.
Not to be outdone in the virtual machine market by VMWare, Microsoft
released Virtual Server 2005 in an effort to go head-to-head with the x86
virtual machine leader. Adding this server component to its desktop
product, Virtual PC, Microsoft is marketing Virtual Server 2005 as a way to
increase efficiency and reduce operating expenses.
Uses for virtual servers
In many environments, the IT department buy and use separate physical
servers to keep processes and applications separate and to reduce the
chances of a single application failure taking down multiple services. In a
lot of cases, this is a good idea but results in high-powered (and often
expensive) servers being used to serve up applications with fairly minimal
requirements. One way to reduce this overhead and use hardware more
efficiently is to employ a single server with multiple operating systems
running simultaneously to provide services that have fairly low-to-medium
Another reason to consider a virtual server rollout has to do with
infrastructure management. Some environments operate at a fast and
furious pace, and the time required for a server rollout is money lost. Or,
light staffing results in additional server rollouts holding up projects.
Regardless of the cause of the problem, a product such as Virtual Server
2005 can help to mitigate these dilemmas with powerful management tools
that make rolling out new virtual machines a breeze.
Virtual server solutions can be a boon for development environments.
While individual developers would probably be able to make excellent use
of the desktop product, Virtual PC 2004, testing and other staging servers
can be easily provisioned on virtual servers with a minimal number of
physical servers required. Imagine being able to test five different
applications on a single physical server while at the same time being able
to run all of the applications separately and safely. Enter Virtual Server
Microsoft virtual machine product line
Microsoft's virtual machine product line consists of two primary products:
Virtual PC for both Windows and Macintosh systems (a desktop
application) and Virtual Server 2005, a server version of the application.
Virtual Server 2005 is further broken down into the Standard and
Microsoft's desktop virtual machine product, Virtual PC, is available for
both Windows and Mac computers. Microsoft acquired this product (as well
as the beginnings of the Virtual Server 2005 product) from its acquisition of
Connectix in 2003.
The Windows version of this product, Virtual PC 2004, can run on
Windows XP Professional, Windows 2000 Professional, or the tablet
version of Windows XP. It requires at least a 400 MHz processor, but, in
reality, you'll want to use something much faster if you plan to do anything
truly productive with the guest operating system and not bring the host
machine to a crawl.
As for RAM, you'll need at least 128 MB on the host machine just to run
Virtual PC. Additional RAM is required for each virtual machine you install.
I recommend no less than 1 GB of RAM for Virtual PC. This will let you
comfortably run a couple of virtual machines and not kill the host. The host
installation also requires 2 GB of disk space. Virtual PC 2004 can use up
to 3.6 GB of available host memory allocated to guest machines.
The supported guest operating systems—the ones that run inside the
virtual machine—can be any of the following: any version of Windows later
than Windows 95; DOS 6.22; or OS/2 Warp 4 Fix Pack 15. While Microsoft
supports only the operating systems listed, other x86-based operating
systems, including Linux and Novell NetWare, can also be used under
Virtual PC. Various newsgroups can be invaluable if you're trying to get a
specific Linux distribution running under Virtual PC and you're having
Table A lists the supported guest operating systems along with the RAM
and disk space requirements of the host for each guest. Remember that
these requirements are above and beyond those for Virtual PC on the
host. These values are just the recommended minimums. If you have
additional RAM and disk space on the host, you can allocate more
resources to the guest operating system to improve its performance.
Guest operating system RAM Disk
Windows XP Professional 128 MB 2 GB
Windows XP Home 128 MB 2 GB
Windows 2000 Professional 96 MB 2 GB
Windows NT Workstation 4.0 SP6 64 MB 1 GB
Windows Me 96 MB 2 GB
Windows 98SE 64 MB 500 MB
Windows 95 32 MB 500 MB
MS-DOS 6.22 32 MB 50 MB
OS/2 Warp 4 Fix Pack 15 64 MB 500 MB
Operating systems supported by Virtual PC 2004, along
with host system requirements
As for Macintosh hosts, before you buy Virtual PC 7 (the latest Mac
version), you need to select your version. Microsoft sells five editions of
Virtual PC 7 for the Mac. With the exception of the Upgrade edition and the
Standard edition, each of the other three versions comes bundled with a
Windows license. You can choose from Windows XP Pro, Windows XP
Home, or Windows 2000 Pro licenses. If you already have a legal copy of
Windows, you can just buy the Standard version that includes no Windows
Virtual PC 7 includes support for the G5 processor and for Mac OS X 10.3
for better performance. With this product, you can even use peripherals
that are designed for Windows only. That said, your Mac must have at
least a G3 processor running at 700 MHz and at least 512 MB of RAM, as
well as Mac OS X 10.2.8 or higher. Virtual PC on a Mac has to actually
emulate PC hardware rather than being able to just virtualize it, so the
system requirements are a little higher.
The only guest operating systems supported on the Mac version of Virtual
PC are Windows XP and Windows 2000. You can run other x86-based
operating systems (Windows 98 or Linux, for example). However, some
features, such as the Virtual Machine Additions—the software that
provides critical drivers—may not install.
Virtual Server 2005
Microsoft's newest foray into the virtual machine world came in the third
quarter of 2004 with the introduction of the first release candidate of Virtual
Server 2005, an industrial-strength virtual machine solution on par with
VMWare's GSX Server product.
Like VMWare GSX Server, Microsoft's Virtual Server 2005 product
differentiates itself from the workstation version in a number of ways. First,
and most importantly, is the issue of scalability. Whereas the Virtual PC
workstation product can use up to only 3.6 GB of RAM and a single
processor, and can run only a few virtual machines at once, the server
product can scale up to either four or 32 processors, depending on which
product edition (Standard or Enterprise) you select. This processor
limitation is the only difference between the two editions of the program.
Further, the server product supports up to 64 virtual machines on a single
virtual server platform.
The host server for any significant virtual server implementation requires
substantial RAM in order to support both the host operating system as well
as serve the needs of the individual guest operating systems. Virtual
Server 2005 supports a whopping 64 GB of RAM shared among all of the
virtual machines. However, each virtual server is limited to using 3.6 GB of
Even though it supports up to 32 processors, at present, Virtual Server
2005 doesn't allow you to assign multiple processors to a virtual machine.
Currently, guest operating systems can see only a single processor,
although multiple guests can share a single processor. Intel's
Hyperthreading technology does not virtually increase the number of
physical processors, either.
Virtual hard disks (VHDs)
Virtual Server 2005 (and Virtual PC, for that matter) encapsulate the entire
contents of each virtual machine into VHDs—basically files on the host
system. Since the VHD is just a single file on the host system, it can easily
be moved to another virtual server and brought up with no reconfiguration
necessary. Compare this to moving your physical server to new hardware.
Since a lot of hardware isn't identical, driver changes are sometimes
required, and this can be a painful process. With Virtual Server 2005, the
virtual server hardware emulated on one host operating system can easily
be mimicked on another host operating system so that there's no need to
reconfigure guest installations when they're moved between hosts.
VHDs are created with the management tools shipped with the product.
Each virtual machine has a maximum storage potential exceeding 56
terabytes (yes…terabytes). A virtual machine can be assigned up to 32
VHD files, each up to 128 GB. The VHDs are connected to the virtual
machine via virtual IDE and SCSI controllers. Once you start using virtual
machines, you'll see exactly how much they act like real hardware.
Other hardware provided
Machines running inside a Virtual Server 2005 partition are provided a
variety of hardware. Some of it is hardware actually present in your
computer such as RAM, processor power, and disk space. Other hardware
critical to the proper functioning of a server, such as printer ports, network
adapters, BIOS, serial ports, and other typical devices, are provided in a
slightly different way. Obviously, if you have 32 virtual machines running
on a single server, you probably don't have 32 printer ports, 32 serial ports,
32 BIOSs, 32 network adapters, and so on. Also keep in mind that each
virtual server can have more than one of each of these devices. For
example, a virtual server can have up to four virtual network adapters.
Virtual network adapters don't need to be associated with actual hardware
on the host, although the virtual servers will make use of the host's network
adapter for network communication.
Since not all of this hardware can be provided, Virtual Server provides
virtual devices instead. The virtual machine can see and make use of the
virtual hardware, but you determine where it all comes from. In the case of
the network adapters, you can tell the virtual machine to communicate
directly with the LAN and bypass the host. Obviously, the traffic has to go
through the host at some point, but the guest operating system doesn't
need to know that.
Other hardware, such as virtual floppy drives, can be pointed at physical
host hardware or at image files. Another great example of this ability is with
CD-ROM drives. You can either point a virtual server's CD-ROM drive at
one of your physical CD-ROM drives or at an ISO image, which becomes
an IDE or SCSI device in the virtual machine.
Host operating systems
Unlike the workstation version, Virtual Server 2005 runs only on Windows
platforms. In fact, as of this writing, only Windows Server 2003 is usable as
a host operating system, and I wouldn't expect that to change.
Guest operating systems
Being a Microsoft product, Virtual Server 2005 is obviously optimized for
Microsoft operating systems including Windows Server 2003 (Web,
Standard, and Enterprise editions), Windows Small Business Server 2003,
Windows 2000 Server and Advanced Server, and Windows NT 4.0 SP6a.
However, Virtual Server 2005 will run any x86-based operating system,
even various Linux flavors and NetWare, Solaris for Intel, and OS/2.
The right product for the right problem
With a push to lower administrative overhead, and with IT desires to make
jobs easier on less hardware, products such as Virtual Server 2005 have a
healthy future ahead of them. Depending on your organization's needs,
both Virtual Server 2005 and Virtual PC 2004 can get you on the road to
exploiting the power of virtual machines.