APC 400kW1MW User Manual download pdf (Page 22)

CHAPTER 3 - Data Center Power

The required quality of a data center’s power is essential due to society’s high reliance

on the services that data centers provide and the consequently extreme costs of downtime.

This section of the report will discuss the required reliability and availability as well as the typical

distribution design of data center power. The implementation of fuel cells into data center

primary and secondary power supplies will also be presented.

3.1 Reliability & Availability of Power

Power of high quality is essential for data centers. If a data center experiences

downtime, not only will the owner suffer financial losses, but also customer dissatisfaction,

decreased brand loyalty, and less potential for future business [27, p. 712]. One hour of

downtime can cost $6.45 million for a broker firm and $2.6 million for credit card sales [27, p.

712]. With these statistics, it is understandable that power reliability is a primary issue for data

center management [28, p. 808].

Reliability is defined as the ability of a component or system to perform its intended

function during a specific time [27, p. 713]. The target for data center reliability is “six nines,” or

99.9999% [28, p. 810]. In order to achieve this high level of reliability, a redundant system is

required. An analysis comparing the costs of redundant equipment versus the business losses

needs to be done in order to determine how much the owner should spend on redundancy [27,

p. 712].

Availability is defined as the ratio that describes the percentage of time that a component

or system can perform its required function [27, p. 712]. Voltage variations affect computer and

communications equipment just as if there were a power outage. Therefore, availability must

include the time that the power supplied would not be within the tolerances of the IT equipment.

Utility services typically do not include voltage sags, short power outages of less than a minute,

or long power outages caused by natural events in their availability calculations. Because IT

equipment is typically not able to immediately recover after a lack of power supply, additional

downtime will be experienced, and data center owners need to be aware of this possibility. In

fact, on average, it takes 16 hours for an internet data center to “completely resume normal

operations due to the complexity of re-booting computers, re-starting processes, re-establishing

high-speed communication links, re-synchronizing large corrupted databases, and so forth” [29,

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APC 400kW1MW User Manual Page 22