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What to know when choosing a desktop virtualization type

Desktop Virtualization primarily comes in two forms: Type 1 and type 2. Making a decision between the two is more strategic than technical.

In an environment utilizing type 1 virtualization, the virtualization software is the base operating system (OS) which is installed first onto the subject PC. Additional operating systems, such as Windows or Linux, run as guests on top of the virtualization software.

Type 1 makes the most sense for the enterprise, where administrators need to deploy standardized operating systems to disparate systems. With hardware running type 1 virtualization, administrators can create deployment packages and quickly deliver "complete virtual systems" to systems running the type 1 hypervisor. Backups are also eased and an additional layer of security can be added to end-client devices. Type 1 proves to be most suited for the data center and server class systems, but is starting to find its way to desktop systems.

Examples of type 1 hypervisors include Oracle, VMware's ESX Server, IBM's LPAR, Microsoft's Hyper-V, Sun Microsystems' Logical Domains, TRANGO and Xen.

Vendor Product Hardware For more information
VMware ESX Server Intel & AMD

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http://www.vmware.com/products/vi/esx/
IBM LPAR IBM P Series http://www-03.ibm.com/systems/i/os/
Microsoft Hyper-V Intel & AMD CPUs http://www.microsoft.com/windowsserver2008/en/us/hyperv-main.aspx
Sun Microsystems Logical Domains Sun Cool Threads Servers http://www.sun.com/servers/coolthreads/ldoms/index.jsp
VMware Trango Smart Phones Portable devices http://www.vmware.com/technology/mobile/index.html
Citrix XEN Server Intel & AMD http://www.citrix.com/English/ps2/products/feature.asp?contentID=1686939

Type 2 uses a different approach: A primary OS is first installed on the PC (Windows, Linux, MAC, etc.) and then virtualization software is installed on to the primary OS. That virtualization software creates a hypervisor environment that can run guest operating systems. Type 2 proves to be beneficial for those seeking to run guest operating systems occasionally on their local PC or laptop. It is also the basis for Windows XP compatibility mode found on Microsoft's forthcoming Windows 7 operating system. Windows XP compatibility mode works by creating a virtual Windows XP system on top of the Windows 7 OS by using a type 2 hypervisor.

Examples of type 2 virtualization include VMware Workstation, VMware Fusion, QEMU, Microsoft's Virtual PC and SWsoft's Parallels Workstation and Parallels Desktop.

Vendor Product Hardware For more information
VMware VMware Workstation AMD & Intel http://www.vmware.com/products/ws/
VMware VMware Fusion Macintosh http://www.vmware.com/products/fusion/
QEMU QEMU AMD & Intel http://www.qemu.org/
Microsoft Virtual PC Virtual PC AMD & Intel http://www.microsoft.com/windows/virtual-pc/default.aspx
SWsoft Parallels Workstation AMD & Intel http://www.parallels.com/
SWsoft Parallels Desktop Macintosh http://www.parallels.com/

Regardless of the virtualization type chosen, desktop virtualization offers several advantages over traditional single OS deployments:

  • Cloning and deploying virtual machines is much easier than a traditional workstation deployment

  • Virtualization helps to "normalize" the hardware and offers virtual hardware drivers under the hypervisor that eliminates incompatibilities between hardware platforms

  • Virtual machines prove easier to backup than traditional desktop PCs
    • Backups can be accomplished by simply making a copy of the virtual hard drive (VHD) file on a PC

  • A virtual machine can be moved quickly to replacement hardware by copying the VHD file to another system running a compatible hypervisor

While virtualization does offer several benefits, there are a few drawbacks that administrators need to know about:

  • Virtualization can make monitoring licenses more complex
    • Administrators will have to track how many licensed copies of OSes and applications are in use to validate that licenses are not being violated

  • Most virtualization solutions impact performance
    • Slowing down a desktop PC may create some end-user angst

  • Administrators have to consider the costs involved with virtualization
    • While many of the above mentioned vendors offer their virtualization solutions for free, others do charge for the hypervisor software
    • Beyond software cost, there are management and deployment costs that should be accounted for to calculate the ROI of a virtual desktop deployment

Administrators that are serious about virtual desktops should also look at VDI and connection broker solutions to ease the management hurdles and keep track of who is using what when.

ABOUT THE AUTHOR:   
Frank Ohlhorst
Frank Ohlhorst is an IT journalist who has also served as a network administrator and applications programmer before forming his own computer consulting firm.

This was first published in August 2009

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