Virtual desktops are based off virtual OS images -- including "gold" Windows images -- and fewer images can mean significant cost savings. But how?
Beyond a reduction in the amount of hardware needed to support users, additional cost savings from virtual desktop infrastructure (VDI) rely on its ability to automate the creation, management and maintenance of OS
Managing VDI image customization
Both management and support of desktop images have long been time-consuming and labor-intensive. We start the VDI image process by creating a read-only base user desktop image suitable for a large group of users. Though this base image may be locked, users can still customize their Windows desktops and even install new application software and patches to that base image.
VDI supports end-user customization by storing unique user data separately, either on a local hard drive, shared network drive, or virtual drive within the VDI itself. But as users install additional applications and patches, the amount of custom user data begins to grow, which can create performance issues as more personalized data gets loaded every time a user boots a virtual desktop -- plus capacity issues for VDI storage.
One solution is to rebuild and redeploy the base image as application and OS patches are released. However, when an update occurs in the base image, that new image may be incompatible with users' existing customized data. Any time a base desktop image is updated, that can force users to reinstall or reconfigure third-party applications they've installed.
A few well-known vendors take different approaches to this problem.
Windows Server 2012 image management
Microsoft's image management and monitoring capabilities allow IT to see the health of an entire VDI environment at a glance.
Microsoft Windows Server 2012 offers a single centralized console for ongoing VDI tasks such as image updates and patching. Server 2012 also includes a set of tools to assist in creating user pools -- users with common application requirements -- as well as image management tools to preserve users' custom settings and data. Plus, you can create base images that will populate personal and pooled Windows desktops. Note that Windows Server 2012 does not currently offer native support of image layering, as do the following two VDI image management tools.
Also, the Microsoft PowerShell scripting language allows VDI administrators to automate routine image management tasks. Microsoft includes several "what if" tools to help admins gauge the performance impact of changes to resource allocations and simultaneously deploy new images to multiple VDI servers.
VMware Mirage is a reality
VMware's Horizon Mirage product tackles base image updates by splitting images into a series of layers. Here's how this works: IT creates one or more base OS layer image, along with driver library images and application-layer images. Mirage supports multiple driver and application image layers that can be deployed to different sets of users based on common device or application requirements. You can create one application-layer image for sales, a different one for executives, and so on.
More on VDI image management
Comparing nonpersistent and persistent VDI
Get to know four virtual disk formats
How golden image customization can improve performance
Those application images may be updated at will with patches or new versions of that application-layer image without disturbing the other layers of images. Better yet, Mirage makes updates to image layers transparent to users because new layers are deployed only when IT chooses to do so.
Mirage can also perform ongoing backups to the VDI for individual user desktop changes, using snapshots of user data uploaded on a configurable schedule. Once a roaming user reconnects to the corporate network, image layer updates and user data synchronization occurs automatically.
Unidesk VDI image management delivers
Unidesk seamlessly manages VDI environments, including VMware View and Citrix XenDesktop. Early on, Unidesk recognized the issues with managing virtual desktops, users' custom data and the proliferation of base images due to "image creep" -- the tendency to create additional base VDI images for each use case -- which often resulted in a plethora of base images when just one golden image is preferable.
Unidesk VDI image management offers more capabilities than Horizon Mirage. VDI administrators can divvy up device drivers and applications into discrete image layers that can be deployed and managed as separate entities. This lowers the risk that changes to one layer might adversely affect the continued operation of other layers in the image stack. Unidesk also keeps a history of all changes, updates and patches to image layers. If you later discover changes introduced to a layer via a patch or other update causes unforeseen problems, Unidesk allows admins to roll back to a previous version of an image layer.
About the authors:
Ed Tittel is a 30-plus year IT veteran who's worked as a software developer, networking consultant, technical trainer, writer and expert witness. Perhaps best known for creating the Exam Cram series in the late 1990s, Ed has contributed to over 100 books on a variety of computing topics, including numerous titles on information security and HTML. Ed also blogs regularly for Tech Target (IT Career Jump Start, Windows Enterprise Desktop), Tom's IT Pro, UpperTraining.com, and PearsonITCertification.com.
Earl Follis is a long-time IT professional who's worked as a technical trainer, a technical evangelist, a network administrator, and in other positions for a variety of companies that include Thomas-Conrad, Tivoli/IBM, Nimsoft, Dell and more. He's also contributed to numerous books, including …For Dummiestitles on Windows Server and NetWare, and he's written for many print and Web publications. His primary areas of technical interest include networking, operating systems, VDI and unified monitoring.
This was first published in September 2013