Cost Saving Data Center:
This paper will show that the single largest avoidable cost associated with typical data center and network room infrastructure is oversizing. The utilization of the physical and power infrastructure in a data center or network room is typically much less than 50%. The unused capacity of data centers and network rooms is an avoidable capital cost, and it also represents avoidable operating and maintenance costs. This paper is constructed in three parts. First, the facts and statistics related to oversizing are described. Next, the reasons why this occurs are discussed. Finally, an architecture and method for avoiding these costs is described.
Facts and Statistics Related to Oversizing
Anyone in the Information Technology or Facilities business has seen unused data center space and observed unused power capacity or other underutilized infrastructure in data centers. In order to quantify this phenomenon, it is important to define the terms used for discussion.
Modeling assumptions
In order to collect and analyze data related to oversizing, APC surveyed users and developed a simplified model to describe infrastructure capacity plans for data centers. The model assumes the following:
- That the design life of a data center is 10 years
- That a data center plan has an ultimate Design Power Capacity and an Estimated Start-Up Power Requirement
- That in the typical lifecycle of a data center the Expected Load is estimated to increase linearly from an expected start-up load and achieve a final ultimate value halfway through its expected lifecycle.
The model as defined above gives rise to the planning model shown in Figure 1. This is assumed to be a representative model for how systems are planned.
The Figure shows a typical planning cycle. The Installed Capacity of the power and cooling equipment installed is equal to the Room Capacity. In other words the system is completely built-out from the beginning. The plan is that the Expected Load of the data center or network room load will start at 30% and ramp up to a final Expected Load value. However, the Actual Start-Up Load is typically lower than the Expected start-up Load, and it ramps up to an ultimate Actual Load, which is considerably less than the Installed Capacity (note that the Nameplate Power Capacity of the actual equipment installed may be larger than the Installed Capacity due to redundancy or user-desired de-rating margins).
Data from actual installations
To understand the actual degree of oversizing in real installations, APC collected data from many customers. This data was obtained by a survey of actual installations and through customer interviews. It was found that the start-up Expected Load is typically 30% of the ultimate Expected Load. It was further found that the start-up Actual Load is typically 30% of the start-up Expected Load, and that the ultimate Actual Load is typically about 30% of the Installed Capacity. This data is summarized in Figure 1. The average data center is ultimately oversized by 3 times in design value. At commissioning, the oversizing is even more dramatic, being typically on the order of 10 times.
Excess cost associated with oversizing
The lifecycle costs associated with oversizing can be separated into two parts: The capital costs and the operating costs.
The excess cost associated with capital is indicated by the shaded area of Figure 1. The shaded area in the figure represents the fraction of the system capacity that is not utilized in an average installation. The excess capacity translates directly to excess capital costs. The excess capital costs include the costs of the excess power and cooling equipment, as well as capitalized design and installation costs including wiring and ductwork.
The power and cooling systems in a typical 100kW data center have a capital cost on the order of $500,000 or $5 per Watt. This analysis indicates that on the order of 70% or $350,000 of this investment is wasted. In the early years, this waste is even greater. When the time-cost of money is figured in, the typical loss due to oversizing nearly equals 100% of the entire capital cost of the data center! That is, the interest alone on the original capital is almost capable of paying for the actual capital requirement.
