This blog is an excerpt from the Unidesk eBook Ten Quick Tips for Scaling VMware Horizon View.
Those who have successfully virtualized their servers often go into their desktop virtualization project assuming the cost savings of VDI will be similar. That's not the case.
Server virtualization was easy to cost‐justify: consolidate a large number of under‐utilized small servers down to a small number of fully utilized, virtualized big servers. Save money.
Desktop virtualization is harder. By the time you add up the cost of servers, storage, and thin clients, then factor in licensing for software, the best you're likely to do is break even on capital costs compared to buying new PCs.
This is why many VDI projects have had trouble scaling - IT managers have been unable to educate senior IT management on cost savings of VDI beyond the soft benefits of enhanced mobility and security.
If you quantify cost savings, expanding your VDI deployment will be a much easier sell to your internal decision‐makers. Here's how to focus on the two primary sources of cost reduction: Energy Savings and OpEx Savings.
How To Do It
Let's look at energy savings first. Thin (or zero) clients use 5‐14 watts of power per hour. PCs use 65‐250 watts of power per hour. The difference comes from the thin clients having no hard drives, no moving parts, minimum processing power and a relatively small amount of RAM. Armed with this knowledge and some assumptions, it's easy to show that VDI will save your organization a considerable amount in yearly energy costs.
Let's assume thin clients and PCs are in active use about 9 hours a day, 230 work days a year (excluding weekends, holidays, vacation, and training). The rest of the time they should be in sleep mode to conserve energy.
To be fair, let's account for the servers that will host your virtual desktops. A server hosting VDI workloads will consume 450‐650 watts of power per hour, and host 60‐100 virtual desktops (desktop density). Unlike PCs and thin clients, servers are in active use 24x7x365, since one of the key benefits of VDI is anywhere, anytime access to desktops.
Now add in your cost of electricity in KWH for your location, and you can calculate the savings using the following formulas.
Here's a calculation for PC costs per year:
Here's a calculation for VDI energy costs per year:
Assuming an electric rate of $.20 per KWH, the energy costs for 1,000 PCs would be about $33,000 USD per year. By comparison, the energy costs for 1,000 virtual desktops would be about $15,800. Over the 4-year lifespan of a PC, that's a savings of almost $70,000 in favor of VDI.
Don't like math? Check out our more advanced VDI Energy Savings Calculator.
Operational Cost Savings
Calculating the operational cost savings of VDI vs. PCs is a bit more involved. But the results are often staggering in VDI's favor. The free eBook Desktop OpEx Savings: The Key to Cost-Justifying VDI explains in simple terms how to calculate potential savings.
The eBook looks at three areas - Operating System image management, application delivery, and desktop support - and compares how these operations are carried out in the physical PC world, traditional VDI environments, and VDI environments that are managed by new desktop layering software.
The VDI business case spreadsheet mentioned above for energy savings also calculates the OpEx savings. When you put the two together, VDI becomes a no‐brainer, and a much easier sell to your decision-makers.