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Introduction
Predicting and measuring Total Cost of Ownership (TCO) for the physical infrastructure for network rooms and data centers is required for Return-on-investment analysis and other business decision processes. In addition, an understanding of the cost drivers of TCO provides insight into opportunities to control costs. Many users are surprised when they consider that the TCO for physical infrastructure may be comparable to or larger than the TCO of the supported Information Technology equipment.
In this paper, a method for determining TCO of physical data center and network room infrastructure will be described. In this context, the physical infrastructure means all of the facility equipment needed to provide power, cooling, and physical protection of IT equipment, but not the IT equipment itself.
There are no recognized standards for measuring the TCO of the physical infrastructure of data centers. Simple methods of summing various capital and operating expense items do provide insight into total cash outlay, but they do not account for the utilization of the equipment.
Consider the case of two data centers, each 100kW capacity and built identically; in one case the data center is fully utilized to 100% of the space and power capability; and in the other case the data center has only a single rack with 2kW of Information Technology equipment. While the cash cost of operating these two facilities over their lifetime is comparable, the useful return on that investment is totally different. In the totally utilized case, the TCO of the data center is spread over a large amount of Information Technology equipment providing useful services. In the lightly utilized case, the entire burden of the expense of the physical data center infrastructure must be borne by the single rack. When TCO of physical data center or network room infrastructure is measured from the point of view of the useful work performed, namely how much IT equipment is supported, underutilization can drive extraordinary cost.
This paper will show that when TCO is viewed from the point of view of the useful work performed, the single largest cost driver of TCO for data center and network room physical infrastructure is the unabsorbed overhead cost of underutilized infrastructure. The highest return investment that the average data center operator or specifier can make in relation to physical infrastructure is in rightsizing. The practical and feasible financial return from a rightsizing strategy is quantified.
Relating TCO to the useful work performed
Most attempts to quantify TCO end up expressing TCO per data center, per square foot of data center, or per kW of data center. These metrics are not useful when considering the useful work performed, and are unhelpful to Information Technology staff in determining project ROI. They don’t at all help an individual attempting to determine the TCO associated with the deployment of a new IT application in an existing data center or network room environment.
One measure of physical infrastructure, which is commonly understood by both facility and IT personnel, is the rack itself. The power, cooling, and area requirements of a rack are reasonably well standardized from a facilities standpoint. The amount of IT functionality and equipment that can fit in a rack is reasonably well understood from an IT standpoint. This has lead to the concept of expressing facility infrastructure in terms of "Racks" or "Rack Units", which is now beginning to gain wide acceptance.
For this purpose, the term "rack" refers to an open frame rack or rack enclosure, and it also refers to proprietary cabinets such as mainframe computers and large disk systems.
Research shows that the typical data center is only utilized to 30% of its capacity. While some data centers are utilized to 90% or more of capacity, there are similar numbers utilized to only 10% of capacity.
Furthermore, the utilization of a data center varies during its lifetime according to a relatively consistent pattern. Fraction of utilization, and its variation with time, is an important input into a TCO model. In this paper, the typical model of Figure 1 is used. For a more complete discussion of this topic, consult APC White Paper #37, "Avoiding Costs from Oversizing Data Center and Network Room Infrastructure".
When TCO is expressed in a per-rack basis, the total cost of the data center or network room is allocated across the utilized racks. In this way, no unallocated overhead costs are created, and costs associated with data center or network room physical infrastructure can be more accurately and directly related to the IT infrastructure.
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