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Storage and the virtual desktop: Managing desktop images and user data

Get a better handle on desktop virtualization images by implementing SAN or NAS for easier storage.

The cost of provisioning data center storage is one of the issues that has IT thinking twice about the move to virtual desktops from physical desktops and laptops. Even though managing all the remote desktops and the associated data can be very expensive in personnel time and efforts, you have to admit that the disks that come with desktops and laptops are, well, cheap.

Not so with SAN or NAS, which is not technically required to implement a desktop virtualization infrastructure (VDI). However, it is highly recommended to gain the availability and dynamic load balancing capabilities that come with implementing desktop virtualization with networked storage.

So how do you use this more expensive storage infrastructure to minimize capital expenditures and gain the manageability and flexibility that comes with VDI? This tip will cover the procedures and technologies available for managing the number of images that can be stored on disk, as well as storage virtualization technologies that you can use to minimize the storage impact of moving desktops to the data center.

Nothing beats good and smart planning prior to an implementation to glean the greatest benefit. Part of the planning has to do with process and the other part of the planning has to do with researching technologies that aid the implementation goals.

On the process side, I recommend separating out the desktop application from the desktop operating system(s). This will streamline the base operating system "golden image(s)" and reduce the number of separate golden images required. Once the golden images have been created, they become the templates for every desktop operating system.

If you are implementing VDI using Citrix XenDesktop, then you can stream the same operating system image to many desktops, significantly reducing the amount of disk space required for OS images. This has the added benefit of greatly reducing the management required -- changes are made to one image in one place and automatically propagated to all the desktops on reboot. If you are using VMware VDI, the use of templates and PXE booting can also reduce the OS image storage requirements.

By separating the applications from the desktop operating system, you can also reduce the footprint required by application images. Rather than duplicating the same application images within many desktops, you can use application virtualization and streaming, such as Citrix XenApp, Symantec Altiris SVS and Microsoft App-V, to create one image, manage and maintain the one image and stream the one image to many desktops. Something similar can be created using VMware ThinApp by locating the application image on NAS storage where many desktops can access the image using NFS or CIFS.

Finally, storage requirements and growth can be managed by using storage virtualization solutions that incorporate deduplication and/or thin provisioning. Deduplication came from the backup and recovery market to reduce the amount of duplicate data being backed up. More recently it has been incorporated into storage and storage network solutions. Deduplication removes copies of identical images so there is only one real image with many pointers to that image. This is an excellent way to reduce storage requirements, as much as 50%, especially in an environment where large files are emailed or copied to many users. Storage vendors that support deduplication within their solutions include NetApp Inc., Xiotech Corp. and FalconStor Software Inc.

Thin provisioning allows the administrator to tell the system it has more storage than what is actually provisioned for that system. This allows IT to grow the storage as it is used rather than having to provision large amounts of storage that sit empty for long periods of time. Examples of thin provisioning solutions are Dell's EqualLogic, HP/LeftHand Network's SAN/iQ and DataCore's Virtual Capacity.

So if the storage requirements of a VDI implementation are giving you pause for thought, the combination of smart planning and effective use of available technologies can go a long way to reducing the amount of storage actually required for the implementation and thereby reduce the cost. That, along with the reduced desktop and application image management costs and increased data and desktop security, provide a compelling case for moving to a virtual desktop infrastructure.

About the author: Anne Skamarock, director of research at Focus Consulting (, has been involved with computers and associated technology for nearly 30 years. She started her career as a software engineer developing custom scientific codes and as a Unix systems administrator. She moved to the systems vendor side and worked as a software engineer and in technical sales, marketing and management for both large and start-up systems and storage companies, including SRI International, Sun Microsystems and StorageTek. For the past seven years, Anne has worked as a market analyst focusing on the convergence points around systems, storage and software. Skamarock writes extensively for TechTarget's,, and others. She co-authored Blades and Virtualization: Transforming Enterprise Computing While Cutting Costs (Wiley). FOCUS recently finished a FOCUS Landscape Series on Desktop and Applications Delivery Alternatives.

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