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Desktop Virtualization TCO Comparison a Hot Topic

I got lots of feeback on my last blog, "Desktop Virtualization vs. Physical Desktops: Which Saves More?" Paulk from SF asked: 1. Won't there be client OS licensing costs for the virtual desktops or is that covered in the desktop virtualization software cost? 2. Does the $400/seat client operational/maintenance costs cover the operation and maintenance of the blade servers as well, or just the thin clients?

The answers are: Sure there are client licenses, but considering you have to pay this on physical or virtual, it washes out. So, no point in listing it. Microsoft has also significantly relaxed the VDI licensing; the $400 is just endpoint.

As for Anonymous, who comments: 100K IOPS, really? 15 x 1000 = 15k

My answer is: 100K IOPS is overkill, but keep in mind 15 IOPS per user when everything is running normal. With bootup storms it could go up to 100 IOPS per user. When using AV, if not architected properly it could go up to 100 IOPS per user. So, yes 100k IOPS at the price I am suggesting, it is a catch :)

Mike comments: So if I did the math correctly, you are going to put 60ish virtual desktops on each blade? It better be a pretty basic desktop you are rolling out to get that kind of density at a reasonable performance in my experience. The math starts to break down differently when you need a more robust desktop. So, this analysis could be correct for 1 use case, but not others.

Mike, 60 VMs is easily achievable especially if the idea is to run most apps using TS. However, on a blade with dual socket Nehalem or better Quad or six cores, this density is not a lot. If architected properly intensive applications are I/O intensive, and that can be overcome by offloading the IO and making sure your VMs are properly configured. I have run Sony Vegas at a university with a density of 60 VMs. The bottleneck with these VMs is usually the IO not the processor, so if you have a SAN that is going to perform, aka 100k IOPS, then it should cover your IO profile regardless. That being said, you can always add more servers, the CapEx spend will not change by much.

Adrian from Germany comments with a link to a Brian Madden post, which references a Microsoft study. To Adrian, I say: Microsoft is not necessarily very VDI friendly, even though in their defense that attitude is changing. It is a Microsoft study geared at satisfying Microsoft's interest at the time of writing; there are hundreds of papers from Gartner, IDC and others that prove otherwise.

Nonetheless, I clearly stated that there are no CapEx savings and I am still unclear as to why you guys are still chasing CapEx. At the very least, desktop virtualization and physical rollouts are tied when it comes to CapEx. On the other hand, why do it the traditional way if you can save so much in OpEx and do things differently?

James K. tells us: I've seen 55 Windows XP VMs run successfully on a dual core server way back in ESX 2.5.3. Those were fairly light use systems, but even back then we could get good performance--and that limit of 55 was brought on more by running out of disk than processor or RAM. So, 60 VMs per host is definitely doable on 4 or 6 core processors.

Elias, where are you getting the estimates of yearly operational maintenance for VMs and desktops from? Just wondering if there's an industry-wide average for those numbers from an independent source.

James, thanks for reinforcing the math, it is always a breath of fresh air when someone else has seen similar results. Regarding OpEx, there are numerous Gartner, IDC and Forrester papers that list these numbers, but in all honesty I was modest, the numbers are higher for physical desktop maintenance. Still, I wanted to be fair, so I increased the number for desktop virtualization OpEx and decreased that of physical desktops.

And finally, NBrady notes: There's a third option not addressed here, cloud hosted virtual desktops (as a service). Whitepaper TCO comparison of PCs, VDI and Clous Hosted Desktops.

Absolutely, NBrady. Cloud based desktops are an option, albeit in my opinion still a bit premature. This will become more of a viable and realistic option when companies decide how they are going to embrace the cloud. Most companies like the idea of the cloud but are in flux as to how to approach it, what services to put in it, etc. Once that is identified, then yes I would agree with you. At this point there are challenges, especially with user data and intensive applications, and so on.

Another reader e-mailed me directly and brought up the fact that the cost of desktop virtualization was a little low and maybe I was pricing it based on educational pricing. That is actually true; my bad. Yet, even if we increase the price of desktop virtualization software by $100, thatt would increase the CapEx by $100,000, which is still tied with physical desktops.

Again, CapEx is the wrong area to focus on, as it represents less than 20 percent of the total desktop project. OpEx represents more than 80 percent, so why chase that 20 percent?

CapEx savings were huge in server virtualization, but desktop virtualization is very different. Servers have traditionally had a presence in datacenters and have had all the infrastructure needed. Desktops are decentralized with no presence in the datacenter, so building that presence will cost money.

Thanks for your comments, and keep them coming!

Posted by Elias Khnaser on 03/31/2011 at 12:49 PM


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