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Glossary 297

state’s petroleum consumption. Subsequent research and development
projects focused on topics including environmental effects of energy con-
sumption, development of renewable resources, and advancement of inno-
vative technologies can be found at http://www.nyserda.org/.

NYSERNet (New York State Education and Research Network)
This organization includes a shared data center in Syracuse, NY, mem-
bers of the NYSGrid, members of K-12 schools, colleges, universities,
libraries, and corporate research labs.

NYSGrid (New York State Grid)
A New York State High Performance Computing (HPC) consortium.

OSI (Open Systems Interconnection)
The OSI Reference Model is an abstract description for layered commu-
nications and computer network protocol design.
PDU (Power Distribution Unit)
A device that distributes electric power. Large industrial units are used
for taking high voltage and current and reducing it to more common
and useful levels—for example, from 240V 30A single phase to multiple ptg
120V 15A or 120V 20A plugs. PDUs are used in computer data centers,
stage shows, and in other electrically intensive applications.

PSSC (Products and Solutions Support Center)
The IBM PSSC at Montpelier, France, is focused on benchmarking, per-
formance, and sizing.
PUC (Public Utility Commission)
The general name for the state regulatory body charged with regulating
utilities.

PUE (Power Usage Effectiveness)
PUE = Total Facility Power/IT Equipment Power. A PUE of 1.5 for a data
center is excellent (a green data center), whereas a PUE above 3.0 is con-
sidered quite inefficient. To make a more intuitive metric, the Green Grid
defined the DCiE (Data Center Infrastructure Efficiency) that is the recip-
rocal of the PUE × 100%. So, a DCiE of 100 percent is considered ideal,
whereas a DCiE of 33 percent (a PUE of 3) is considered quite inefficient.
ROI (Return On Investment)
The amount, expressed as a percentage, which is earned on a capital
investment in a project. For example, an investment virtualized for your
data center may have a 33 percent ROI or approximately a three-year
payback.