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New Replacement Policies
The biggest place where you will see cost savings, power reduction, and cooling reduction is
in server consolidation. It’s a no-brainer—the less hardware you have, the less consumption
will occur. When you replace servers, keep these guidelines in mind:

• Replace two or more old servers with a two-way server or dual-core, single-processor
server.
• Replace old servers with a blade based on a low-voltage or mid-voltage processor.
• Replace dual-processor servers with a single, dual-core processor.
• Replace four-way servers with two-way, dual-core servers.
Use Power Management Features
It seems obvious, but some IT managers don’t get it: Use your equipment’s power
management tools. Although electricity usage is reasonably constant, the IT load swings
up and down according to the needs of the system. It can be as much as a factor of three.
By using your equipment’s power management functions and turning off unused
servers, you can cut datacenter energy usage by 20 percent. But it’s not because IT managers
are dimwits—rather, they’re focusing on uptime and performance. In reality, however,
turning on power management features can improve overall reliability and uptime because
it reduces the stress on datacenter power and cooling systems.

NOTE Experiment with your system, however, before turning on any power management features.
In some systems running Linux, for example, waking up an idle server can cause unexpected
behavior.

Get Energy-Efficient Servers
As you upgrade to new equipment, look for energy-efficient servers. They’re using less power
than before, and they’ll probably only get more efficient as new products are introduced.
The first generation of multicore chips resulted in huge reductions in power consumption.
For instance, the Intel Xeon 5100 delivered twice as much performance with a 40 percent
drop in power usage.

Use Energy-Efficient Power Supplies
Probably the biggest wastes of power in the datacenter are the power supplies. Inefficient
units tend to ship with servers, and they aren’t really selected based on how the server is
configured.
Inefficient power supplies can waste almost half of the power before it gets to the server.
Further, every wasted watt is turned into heat, which then requires at least another watt of
power to cool.
Look for power supplies that achieve 80 percent or higher efficiency, even at 20 percent
load. They cost more, as much of this type of equipment does, but they cost less to use. We’ll
talk about power supplies later in this chapter.