Joe, I remember quite well when we tried to calculate the power consumptions of all our servers last time. We needed a new air conditioning and so we required reliable numbers. We sent the specs of all our servers to our specialists. They came up with a number, but they were not really sure. Thus, we just measured the power consumptions for all our servers for one week. It turned out that the number we calculated before was about five times too high.

Of course, you can’t just add all the power specs of the power supplies. That is just the maximum they support. You have to know what your servers actually consume, and this depends on the kind of work they have to do. Ten average servers have more power supplies than a high end-server. This is the reason why your calculation shows such a big difference. In my view, all theoretical calculations about this issue are useless. What we need here is empirical data.

This reminds me about the vendor specs for a laptop’s battery life. My batteries usually only last half of the time they say. I guess, I strain my laptop a little more than those marketing guys who wrote those specs.

As to the link to Intel, this says only something about old vs. new processors. Where is the connection to our discussion? Of course, I can run new CPUs in my ten average servers. However, if you replace old servers with new ones you will always measure higher power consumption simply because the new servers are more powerful. I simply made this experience.

Brian, thanks. The single-point-of-failure argument is certainly the most important disadvantage of server virtualization. But since we are talking about costs, software solutions that can remedy this downside are usually not for free.

Jacob, you’re right, power consumption depends on many factors. But as I outlined in the article there are a couple of factors that increase the power costs in a virtual environment. This is the reason why I think it is mere speculation that virtualization always saves power.

Great two part post on the costs associated with virtualization. Another thing to note as a risk factor of virtualization is the possibility of the consolidated server becoming the single point of failure for business critical applications. This is where fail safe technology needs to come into play so that an organization isn’t affected by the repercussions of downtime. For those interested, Marathon has an ROI calculator which gives decision makers a quick assessment of virtualization’s potential impact on their organization.

Also, it’s not something our customers that just need to run their business (which is not IT related) can profit off.

Software licensing can become more expensive when you use virtualization, e.G. you’ll need more OS licenses and also more application licenses if you for example us Vmotion. Microsoft recently did some adjustments there, but those only apply to VL customers.

Small Businesses can take advantage of Virtualization technology with little cost. Yes we do work in much larger environments than you do which allows us to use Enterprise class Virtualization technology. Our server purchases have been reduced DRAMATICALLY since we began P2V’ing all of the legacy servers that needed to be refreshed. We analyzed our 70 servers and realized how much harddisk space was wasted not to mention underutilized processors just sitting idle. Virtualizing several servers onto one single host allowed us to manage the disk allocation properly, share the RAM, and allow the processor to manage the guests and host seamlessly. We are now using the whole server to its maximum potential. These servers are repurposed database servers that we already had in service. So we didn’t introduce an expensive server to do the job. These existing servers are hosted in a datacenter and standard office building server room. They are quite efficient at self-cooling and never show heat-related issues.

Your work environment is slow to purchase new servers and budgeting appears hopeless. So use VirtualPC which is FREE! or VMWare Workstation. You can run guest systems on a consumer-grade laptop or desktop computer. This is very useful for Developers and consultants who need to test their projects against a real server or workstation. The guest machine running VirtualPC (on your laptop) behaves seamlessly on the network as if it was in the next room.

I would add that Virtualization does save money, it does allow an end-user to standup a Real server in a matter of minutes instead of waiting for the procurement process.

Lastly, it is not for the convenience of IT staff, it is for the brilliance behind virtualization, how it changed the way we do business, how it opened up so many new doors that were closed just a year ago. Embrace it. I am currently building a 3-server Virtual environment for a Disaster Recovery scenario that is impossible to perform on physical servers. We can restore the data offline from tape and really analyze the data integrity, the process, and build confidence in our backup routine.

A quad-core PowerEdge 1950 is capable of handling a load > 10 virtual guests and has two 670 watt power supplies. At 208 volt, this would consume about 6.4 amps total ((670 * 2) / 208). Most of the time the system would not be pulling the full 6.4 amps because of the energy efficiency built into the newer systems. It is common sense that the older systems were not as energy efficienct.
Compare this to the power consumption of 10 physical SC1435 servers with single power supplies (30 amps total).
The raw heat in BTU is 1 W = 3.413 BTUs.
So one server with two 600w power supplies would create 4,095 BTUs/hr.
Ten servers with one 600w power supply each would take 20,478 BTUs/hr.
One ton of air conditioning can cool 12,000 Btu’s per hour.
Therefore, ten servers would require about a 2 ton A/C system, whereas a single 1950 would require just a 3rd of one ton.
I do not think the density of the single system outweighs the benefit of reducing BTU output by 80%.

But i think many of the points go into the direction of extreme enterprises. I recently did a few VMware sales certifications, and there where things like “how many servers does your customers purchase PER MONTH”.

In the small business space were i work, we don’t talk about servers purchases per month – we discuss if we can replace 6 year old machines with new ones. And sometimes even that doesn’t work.

So many of these arguments may be aimed at really, really, big companies. With horribly inefficient processes, where they purchase hundreds of servers per month that do not do anything meaningful – the only reason they exist is The Process.

However, for a typical Small or even Medium Business, where each server purchase is a month long ardous task of trying to get the Powers That Be to agree with spending maybe 50k on new infrastructure, these arguments don’t hold much water.

Virtualization does not save money, as the licenses are almost always as expensive as the servers. Virtualization may allow you to segregate roles, but this is purely to the convencience of IT workers (and would also allow you faster restores, etc.).