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By running multiple virtual servers on one physical server, you’re increasing your
utilization of that machine from 15 percent up to 80 percent.

Hardware Reduction
Consolidation doesn’t just mean that one server can do double-duty. It’s more like a 10-to-1
ratio. For example, the VMware ESX Server can support more than 100 virtual machines.
You can also use the same strategy on storage and network consolidation, thus reducing
more equipment from your server room.
Reducing Operating Costs
According to a study performed by Lawrence Berkeley National Laboratory, the servers in a
datacenter account for about 55 percent of the electricity costs. The remaining power is
spent to support that equipment—Lawrence Berkeley National Laboratory, 2007. So when
you consolidate your equipment, you also need fewer pieces of equipment to play support
roles, so there’s more cost savings there.
Consolidating can save you about US$560 per year per server. So let’s use the simple
math example of consolidating 10 servers into 1. Consolidating 10 servers down to 1
results in a US$5040 savings per year. And that’s at a smallish company. If you have
thousands of servers, you’ll recognize some big savings.
Consolidation also cuts down on the amount of heat generated in your datacenter. But,
like power consumption, it isn’t just the servers that generate the heat, it’s also the equipment
supporting the servers that add to the heat generation. Figure 11-6 shows this.

Repurposing Servers
As part of your green datacenter design process, you should also look at the equipment
you have and evaluate its worth. You might have a systems life cycle that dictates that

Sources of Heat in the Datacenter
Chiller
Humidifier
CRAC
IT Equipment
Power Distribution Unit
UPS PART V
Switchgear/Generator
Lighting

FIGURE 11-6 Servers generate a lot of heat, but it’s the equipment supporting them that adds up to
create more heat.