CASE STUDY | DataTank

Power Requirements and Physical Sizing

In order for meaningful and contextual power consumption and thermal efficiency calculations to be made, a case study was created in order to determine the finite physical dimensions and power ratings of the data centre as a whole.

Data Storage Capacity Requirements

The case study chosen was a University of 10,000 students, where each student would be assigned 1TB of drive storage for their personal use throughout the scholastic year. This drive storage would be stored within the DataTank. The total data storage capacity required by the university was therefore 10PB.

Rack and Core Sizing

The servers storing this data are placed in racks for organisational as well as efficient cooling purposes. The most common racks used in industry are 42U racks. 1U is a unit of measurement used to describe the height of a rack and is equal to 44.45mm. The total height of these type of racks is therefore 1.86m. Each server takes up 1U of space. Each rack will consist of 40 servers and 2U will be allotted to other components necessary for the safe and efficient running of the servers.

Each rack is capable of storing 640TB of data, meaning a total of 15.6 racks will be needed to cater for the entire University. This was rounded up to 18 total racks, in order to allow a student growth rate of 15.2% within the University, while still being able to use the DataTank for storage in the case of future growth. The racks were placed back-to-back, 9 racks to each side. This resulted in a total data storage capacity of 11.52PB.

Each rack has dimensions of 1.67x1x1.86m. This meant the total size of all the racks together, or the core, was 5.4x2x1.86m.

Rated Power Consumption of Core

Each rack consumes 10kW of power and therefore the total energy requirement to power the servers alone was found to be 180kW.

Tank Sizing

The tank radius was sized around the core dimensions. The hoop and longitudinal stress for the thin-walled pressure vessel shaped tank were calculated. Since the hoop stress is always double that of the longitudinal stress, and to maintain uniform thickness across the entire tank wall, only the hoop stress was considered. The tank was assumed to be constructed from grade 316 stainless steel.

The pressure at 100m (maximum operating depth) was found to be around 1MPa. From this value, the size of the core as well as the physical properties of grade 316 stainless steel, the required minimum thickness for the tank wall was calculated and found to be 0.29cm for the hemispheric ends and 0.58cm for the cylinder. This is due to the fact that hemispheres are able to withstand double the stress as cylinders. The overall thickness was therefore taken to be 0.58cm.