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Appendix A
Green IT Checklist and Recommendations 219

will treat servers like you treat lights in your house, turning them
off when not in use or at least turning on only what you need.
Linkage to Total Cost of Ownership (TCO) ensures that green is
part of every decision. Benchmark the entire data center as well as
local areas for continuous improvement. Use commonly accepted
methodologies such as the Power Usage Efficiency ratio (Total
power / IT equipment power = PUE) from Green Grid Consortium
or the Energy-Efficiency ratio.
9. Use the concept of hierarchical storage. Picking the right media
and format for storing data is like picking the right vehicle for a
trip. Not every trip needs an 18-wheeler or a motorcycle. A combi-
nation of disk, tape, and hybrid technologies optimizes the use of
energy while giving your data a secure and extendable home. Tape, a
green storage equipment star, uses the least amount of energy and
should be part of the storage constellation. Disk storage should
be for demanding applications that require frequent updates. The
virtual tape server can mask latency with many applications and is
another green star in the storage constellation. Larger and slower
ptg
disks use less energy, and if their latency can be masked, the energy
efficiencies gained by their use is worth it. For less-demanding apps,
MAID might be appropriate, and the elimination of spinning disks
when not needed can substantially reduce wasted watts.
10. Use the latest equipment. Newer generations of IT equipment are
more energy efficient and give better performance than older IT
equipment. Begin greening your data center with replacing the oldest
and most inefficient equipment first. Newer generations of servers and
storage are built with more efficient power supplies, processors,
memory, and I/O. Just about everything in newer servers and stor-
age provides more performance or stores more data with fewer watts.
We all have experienced how digital cameras have provided more
memory, functions, and better performance in the last five years.
Servers and storage are on similar technology-improvement trajecto-
ries. Servers scale higher in performance while using fewer watts per
logical image. Decommissioning older servers that never were
designed for virtualization or energy efficiency can be one of the
most cost-effective ways to green your data center. Like the gas-
guzzling clunker that needs to be replaced with a hybrid, there are
better ways now to run applications. There is a big difference
between IT and your automobile. The new servers enable you to