VDI is often expensive to deploy -- but doesn't have to be

Follow these optimization tricks to get the cost savings you expected from virtual desktop infrastructure in the first place

Ever heard of the term "money pit"? Dictionary.com defines it as "any entity or venture which requires more money for maintenance and drains financial resources." Some would say that virtual desktop infrastructure (VDI), despite promising great savings over individual desktops, is nothing but a money pit.

That claim seems odd because VDI on paper is incredibly cheap -- so where is the money going? It turns out that much of it is heading toward storage. Three storage factors conspire to goose VDI costs: the excessive amount of storage needed, the lack of storage optimization for VDI, and the fact that storage throughput becomes an expensive performance bottleneck.

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It stands to reason that if you are going to virtualize (centralize) your desktops, then you'll be taking an OS (like Windows 7) designed for local installation and putting it on some form of storage (SAN, NAS, or DAS). You must prepare for heavy disk I/O.

So what do you need to optimize a VDI deployment?

You can start at the end, literally. At the endpoints, use some form of thin/zero client or RDP software to connect to your Windows 7 VDI systems. Make sure you choose clients that perform well and have a solid reputation. You also want to provide a high-fidelity user experience -- at least equal to what's offered locally -- so consider products such as Citrix's HDX and LucidLogix vGPU switching.

Then there's the storage system. When seeking a vendor to provide storage for the VDI client systems, you need to look beyond the SAN, NAS, or DAS. What additional tools is the storage vendor providing to assist with VDI? Likewise, what is your virtualization vendor offering to help optimize storage use and performance?

For example, does your storage vendor help with deduplication? Considering the fact that you plan on using the storage for multiple copies of the same data (the Windows 7 OS), deduplication is one way to reduce the storage capacity requirements of a virtual desktop environment. As one example, EMC VMware uses its "linked clones" capability to address this issue: If you create a base VM template containing the OS and common software, you can create linked clones from that template so that each new VM is only a few megabytes in size compared to several gigabytes of the base image.

Though some of these products address the excessive storage needs for VDI, thus reducing the costs a bit, one issue still remains with regard to performance. Storage throughput, which is measured in MBps (megabytes per second) or IOPS (I/O operations per second), doesn't seem to be reduced much (if at all) by linked clones, nor is it affected by deduplication on the storage device. Even if you've reduced the storage cost through these tools, you may still be spending more than necessary because all your Windows 7 virtual desktops are competing for throughput. That throughput competition creates excessive latency for the users, which IT usually tries to address by throwing more money at the situation via the addition of disks and controllers.

It's an interesting dilemma, and it leaves the door open for creativity. One product, Atlantis Ilio, that I've recently investigated tries to remove the performance barriers by placing itself between the hypervisor and the storage. This "bottleneck fixer" can work with existing techniques (like linked clones) to provide even greater throughput by performing additional deduplication in real time before I/O transactions reach the storage side. Off-loading the IOPS can bring about two results: It can help use the existing storage to hold more VDI desktops, or it can reduce your need to keep throwing more and more storage at the performance issues.

Although the right approach always comes down to the cost-versus-gain calculation, administrators are often too busy to figure it out; they end up throwing money at the problem after the fact rather than brain power before. It takes a lot of effort to determine what you need and what approaches can help enhance performance, so most have not -- and they're bleeding money as a result. Whether you do the work yourself or rely on a consultant, it's time to take a second look at what you have and see if you can put a tourniquet on your VDI deployment. If you haven't yet moved into the VDI world, do the upfront work now so that you get the very real benefit later.

Either way, don't let VDI become a money pit.

This article, "VDI is often expensive to deploy -- but doesn't have to be," was originally published at InfoWorld.com. Read more of J. Peter Bruzzese's Enterprise Windows blog and follow the latest developments in Windows at InfoWorld.com. For the latest business technology news, follow InfoWorld.com on Twitter.

Copyright © 2011 IDG Communications, Inc.

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