On our CitrixLive! webcast last week (Shawn Bass, Rick Dehlinger, Harry Labana, and me), we talked a bit about the power savings you can get with VDI. Or maybe I should say, we discussed whether you could actually get any power savings with VDI. The knee-jerk sound bite is "VDI saves power because lower-power thin clients replace desktops." But does this really save power overall? What about the huge servers on the back-end? What about the changes in heat load? And what about today's desktops which are more energy efficient than ever?
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The (potential) power savings of VDI is something that I've been interested in (and perhaps skeptical about) for a long time. In this article, I'd like to explore the various sides of the issue and start a conversation about what we'd really need to track to figure out whether VDI was actually more "green" than another.
What is "green?"
The term "green" is kind of like the term "virtualization"--it's a trendy buzzword that's used by anyone who can even remotely apply it to their offering. I love the concept of doing things that are better for the environment, but I think a lot of times people do things they think are green without really understanding what they're doing just to make themselves feel better about "helping." And in many cases, people try to apply "being green" to just one aspect of a situation, not realizing they might be making it worse. (Example: Recycling a paper bag is green. Reusing an old bag which causes the paper bag never to have been made is more green.)
I'm not sure exactly when the whole green thing snuck into the desktop world. I distinctly remember an iForum a few years ago where Citrix's Mark Templeton talking about how Citrix technology helped companies be green because employees could work from home. "Not only does it eliminate the commute," Templeton said, "but it also saves on the need to heat and cool of all those employees in a big building."
To me this is a classic example of only looking at a part of the whole scenario. Sure, it's cheaper for the company to only have to house a smaller number of employees. But taken as an entire system, it's actually far less efficient to heat and cool all the individual homes of all the employees than if they were all together in a big building. (Or maybe he meant "green" as in "money," as in it's cheaper to have employees work from home.)
Understanding Power Consumption
I feel like most of the "green" in IT is really about power consumption. (Specifically, minimizing it.) That's fine, and I think most people would agree that consuming less power is generally a good thing. (Both in terms of dollar costs to the company and impact on the environment from the pollution associated with the power generation.)
The problem is that most people don't really understand how power is consumed and how to save it. The biggest misconception is thinking the "rated" power consumption of a device is what that device's power consumption at all times. I can't tell you how many people have used the example of "that desktop has a 400W power supply, so turning it off is the equivalent of turning off four 100W light bulbs." That is false. A 400W power supply means that that power supply has a maximum output of 400W, not that it consumes 400W at all times. The actual consumption depends on things like how many drives you have plugged in, what peripherals you're powering, and how busy your CPU is. (If you want to experiment with finding the "actual" power consumption of your desktop, check out the Kill A Watt energy consumption meter which is available from Amazon.com for about $20.
Does VDI save power?
As sort of a follow up to our CitrixLive! webcast, Rick, Shawn, and I, along with Steve Greenberg, have decided to propose a session about the green impact of VDI at Synergy next year. We're curious about several questions, such as:
- What's the power consumption of a modern desktop computer running several common tasks via Windows 7 installed locally.
- What's the power consumption of a modern thin client device connected to a remote VM running the same tasks via Windows 7.
- What about datacenter blades? Older desktops? Older thin clients?
Does green even matter?
Another interesting aspect of the green thing is that even if we find out that one solution is more green than another, does that even matter? I mean really, who cares? If being green lowers power consumption in a cost effective way, then companies are going to do it! (But they're going to do it not because it's green, but because it saves them money. They couldn't care less whether it was green, brown, or purple--if it saves money, they're doing it!) Other companies think that being green and telling people about it will make people think they're cool and lead to increased sales. So again, they don't really care that they're green, they care about increasing sales.
So do we in the IT world really care about being green? Probably not. We probably just want to lower expenses or increase revenues too.
The problem is that a lot of IT departments don't see power consumption on their budgets, meaning there's no real incentive to save power. Honestly the only customers I know who really care about power are those hitting the maximum power capacity of their datacenters and who need to lower the overall consumption in order to bring in more computing power. But for them the power concern is about server capacity, not about being green.
And then if you actually find an IT department who is charged back for their power consumption, that charge is typically only found in the datacenter--they don't pay for the power consumption of IT devices on employees' desks. So for them, VDI is actually worse because it brings more computing into the datacenter, the electricity of which IT must pay for, where before they didn't.
The biggest bang for the green buck?
Even if VDI does prove to be more green, is it worth it? How much do you have to spend on VDI to get how much green? Is there a better way to spend your money?
The US Secretary of Energy Stephen Chu was recently ridiculed because he said that painting every roof and paved surface white in the US would save carbon emissions equivalent to removing every car on the road for 11 years. (Due to the fact they would reflect heat instead of absorbing it.) This illustrates the great point that sometimes you can save a lot of power by doing little things. For example, instead of buying some fancy new VDI system, maybe if we just configured everyones' monitors to turn off after 10 minutes of idle time and their client devices to go to sleep after 30, perhaps we'd end up saving more power?
Of course while no one is buying and building VDI systems just because they're green, a lot of companies have green mandates and people are using this to help justify a particular architecture or purchase of a new system.
What about you? Does the whole green thing actually affect the IT department in your company? Do you pay for power? Do you do things just because they're green? Do you even care whether VDI is more or less green? Should we spend any more time on this?