How is the IT inventory modelled from basic datacenter parameters ?

How many racks can fit in a given surface ?

nb_racks = IT_surface * racks_per_square_meter_ratio

With:

• racks_per_square_meter_ratio: ratio of how many racks can fit in 1 m² of surface - unit: # racks / m²
• IT_surface: the floor area dedicated to hosting IT devices, aka IT rooms - unit: m²
• nb_racks: the number of racks modelled from previous parameters - unit: # of racks

To compute racks_per_square_meter_ratio we consider a sample rack: 19 inches large, 42 inches deep, (and 42 Units high but this is not relevant in this formula).

Let’s consider:

• rack_width=0.4826 # meters being 19 inches
• rack_depth=1.0668 # meters being 42 inches

The floor area occupied would be:

rack_floor_occupation = rack_width * rack_depth

In our example:

rack_floor_occupation = 0.51483768 # square meters / m²

rack_per_square_meter_ratio = rack_floor_occupation * available_rack_floor_usage_ratio

With:

• available_rack_floor_usage_ratio: a ratio representing the share of an IT room floor area really available for racks (excluding free space for aisles, cooling system equipments, etc.)

We consider a value of 0.5 for this ratio.

Then rack_per_square_meter_ratio = 0.5 * 0.51483768 = 0.25741884

How many servers are modelled in a rack ?

We consider the load_factor parameter as a proxy for the occupation ratio of the racks.

Warning

Using the load_factor both as a ratio for install electric power usage and as a ration for rack occupation is a highly incomplete approach. This will be improved in the future versions of the methodology.

nb_devices = nb_racks * rack_height_units * load_factor

Example

: Let’s consider a Datacenter with 2000 m² of IT floor area and a load_factor or 0.4:

nb_racks = IT_surface * racks_per_square_meter_ratio

nb_racks = 2000 * 0.25741884 = 514.83768 # 515 racks

nb_devices = nb_racks * rack_height_units * load_factor

nb_devices = 515 * 42 * 0.4 = 8652

In the current state of the methodology, we don’t differentiate servers from other kind of devices : network devices, security appliances, etc. This will be improved in the next versions.