Halls — NBD-OM-001

3.1 Data hall layout

Each data hall is a long rectangular room holding rows of equipment racks. The rows are separated by aisles. Every aisle is either cold (air is supplied into it) or hot (air is exhausted from it), and the two alternate across the hall.

The air-cooled halls are identical. A drawing of one is a drawing of all of them. (The densest halls are cooled by immersion instead; Section 5.6.) See Fig. 3.1.

Figure 3.1. A cold aisle: two rows of racks face each other across it. Air is supplied into the aisle and drawn through the equipment. — Figure 3.1 A cold aisle: two rows of racks face each other across it. Air is supplied into the aisle and drawn through the equipment. · drawing ref. NBD-DWG-AISLE

Parameter	Value
Halls	Identical; count recorded in the site register
Layout	Alternating hot and cold aisles
Floor	Raised, on pedestals; services beneath
Ceiling	Cable trays and containment above the racks
Occupancy	None

3.2 Aisle containment

Cold aisles are enclosed at their ends by doors and above by panels, so that the supplied air cannot mix with the exhaust. The doors are sliding and close automatically. They are opened by robotic equipment (Section 4) and by nothing else.

Figure 3.2. Containment for one cold aisle, drawn without its racks. The end doors slide; the roof panels close the aisle from above. — Figure 3.2 Containment for one cold aisle, drawn without its racks. The end doors slide; the roof panels close the aisle from above. · drawing ref. NBD-DWG-HALL

caution

Holding a containment door open disturbs the airflow of the entire row. The facility closes any door left open.

3.3 Racks

A rack is a steel frame of standard width and height into which equipment is mounted. Each rack in the facility is full. Each draws power from two independent supplies and connects to the network by fibre. See Fig. 3.3 and Fig. 3.4.

The rack is the unit in which the facility is planned and counted. When a rack fails, the facility does not repair it in place; it moves the work elsewhere and replaces what failed (Section 4.3).

Figure 3.3. Rack, front elevation, doors open. — Figure 3.3 Rack, front elevation, doors open. · drawing ref. NBD-DWG-RACK

Figure 3.4. Racks, front. Each is full; none is labelled for a reader. — Figure 3.4 Racks, front. Each is full; none is labelled for a reader. · drawing ref. NBD-DWG-RACK2

3.4 Cabling and fibre

Power is distributed to the racks from overhead busways. Data travels between them by fibre, carried in trays above the racks and patched at distribution frames at the end of each row.

The quantity of fibre in a hall is large. Its length, laid end to end, is recorded in the site register. It is not repeated here because the number has no use to a reader.

Figure 3.5. Ladder cable tray, drawn empty. In service it carries fibre (7.3). — Figure 3.5 Ladder cable tray, drawn empty. In service it carries fibre (7.3). · drawing ref. NBD-DWG-TRAY

Figure 3.6. Fibre patch panel at a row end, drawn unpatched. In service every port is in use, and each patch was made by machine. — Figure 3.6 Fibre patch panel at a row end, drawn unpatched. In service every port is in use, and each patch was made by machine. · drawing ref. NBD-DWG-PATCH

3.5 Environmental conditions

Condition	Setpoint	Note
Supply air temperature	Within the equipment's rated range	Set for the equipment, not for comfort
Humidity	Controlled	Prevents static discharge and condensation
Air changes	Continuous	—
Noise	Not controlled	No one is present to hear it
Lighting	0 lux	See 3.7

3.6 Fire suppression

The halls are protected by an inert-gas (clean-agent) fire suppression system. On detection of a fire, the agent is released into the affected hall and the hall is sealed. The agent extinguishes the fire by removing what it needs to burn.

Figure 3.7. Clean-agent cylinders and manifold, stored beside the hall they protect. — Figure 3.7 Clean-agent cylinders and manifold, stored beside the hall they protect. · drawing ref. NBD-DWG-FIRE

warning

The suppression agent displaces breathable air. A person in a hall at the moment of discharge would be at risk. For this reason, discharge is inhibited while a person is detected (Procedure 2.5-1). For the same reason, a person should not be in a hall.

3.7 Lighting

The halls are lit to the level required by code. The lighting has been tested at commissioning and is tested periodically by the facility, which switches it on, confirms that it works, and switches it off.

Apart from those tests, and from the event described in Section 2.5, the halls are dark. The equipment does not need to see. Its status lights, which are small and blue and white, are the only light that normally falls in a hall, and they are not there to be seen either; they are a convention of equipment design, kept because nothing required that they be removed.

performed by	verified by	date	signature

Sign-off fields are provided for regulatory form. No entry is expected.