WestPoint · Hardware · Vertiv
Two servers in a closed cabinet are a one thousand watt heater.
Plant room cabinets, cooling and power. Heat is not a comfort detail: it is what decides whether drives last six years or two, and it is the problem we have most often found unsolved.
What kind of manufacturer it is.
Vertiv · Plant room — Cabinets, cooling and room power. That is: the room, not what goes inside the room.
This house covers three things that go together: the cabinet —with its structure, its doors, its cable management and its lock—, the cooling, from moving air to in-row cooling units, and the power, with backup and metered distribution. And the monitoring of all that: temperature, humidity and door-open sensors that alert over the network.
For a video system that matters more than it looks, because the cabinet is where the whole security of the building lives: recorder, storage, switches, access controllers and intruder panel. It is the place with the most consequences per square metre in the installation, and it is almost always in the room that was left over.
The heat calculation, which is a simple sum.
Everything that goes in as electricity comes out as heat. There are no mysterious losses.
If inside the cabinet there is a recorder, storage, two switches and a backup unit, and between them they draw one thousand watts, that cabinet is putting one thousand watts of heat into the room. It is the equivalent of a small electric radiator switched on at all hours, every day of the year. The sum is that simple and it is almost never done.
What happens next depends on the room. If there is volume and some air change, the temperature settles a few degrees above the corridor's. If it is a small, closed room, it rises until something gives up: in July, with the room at thirty degrees, inside the cabinet it goes past forty without effort.
And the effect is not an immediate fault, which would almost be better. It is that the drives last two years instead of six, the power supplies degrade, the backup batteries wear out at twice the speed and equipment with a graphics card throttles itself so as not to burn. All of that happens without a single error message, and when the faults arrive nobody connects them with the temperature.
Where the air comes in, and the gaps that ruin it.
Here are the two details that mark out a cabinet built by somebody who knows.
Servers take air in at the front and blow it out hot at the back. That forces two things: that the front door really lets air through —a glass door is pretty and it suffocates— and that the hot air at the back does not come round to the front again. When there are several cabinets, that is where the aisle arrangement comes from: all the fronts facing the same cold aisle and all the backs the same hot aisle. Cabinets set facing any old way make each one breathe the hot air of the one next to it.
The second detail is the one nobody expects: the gaps. Every free rack unit left uncovered is a short cut through which the hot air at the back comes back to the face of the equipment, and that ruins the cooling's work. It is fixed with blanking panels, which cost very little and are almost never fitted. The same with the cable entries: if the floor of the cabinet is open, the air escapes where it should not.
And the cabling, which looks like aesthetics and is not. Forty patch leads crossed behind the equipment block the air outlet and turn any change into an hour of risk, because to move one you have to touch thirty. A tidy cabinet cools better and is maintained without fear.
When moving air is enough and when you have to cool.
With a few hundred watts inside and a room with some air change, ventilating well is enough: grilles, fans with filters and a clear path for the air to come in at the bottom and go out at the top. It is the solution in most medium-sized installations and it works if somebody has thought about the air path.
When the consumption goes up —a large recorder, storage with many drives, and more so if there are graphics cards—, ventilating no longer reaches, because you cannot cool a room by blowing the room's own air at it. There you need cooling: room cooling if there are several cabinets, or in-row cooling next to the cabinet if the heat is concentrated in one.
And there is a third decision that gets forgotten: what happens if the cooling stops. A room with a lot of power inside and no cooling heats up in minutes, not hours. That is why the temperature has to be watched with an alert over the network, and it is worth deciding in advance what gets switched off if it reaches a threshold. A thermometer that raises an alert is the best-value investment in the whole cabinet.
Where we would not fit it.
In a small installation, none of this is needed. A recorder and a switch in a well-ventilated wall cabinet, in a cool place, solve the problem. Proposing a plant room for six rack units of equipment is selling kit.
Nor does a cabinet and cooling of this kind make sense if the room chosen is bad to begin with: no ventilation, no space in front and behind to work, with odd humidity or with a pipe running overhead. First you choose the place; the cabinet comes afterwards.
And in an industrial environment with dust —a joinery workshop, an aggregates plant, a milling area— the answer is not to ventilate more, because ventilating means putting that dust inside. There the cabinet has to be closed and cooled, which is a different approach altogether.
What we do with it.
- The sum of the watts of everything that goes inside, with the heat that means, before choosing a cabinet. And the margin for what is going to be added, because something always is.
- The air path drawn out: where it comes in, where it goes out, what door it has and whether the room has air change. With blanking panels in the free spaces and the cable entries closed.
- The temperature sensor alerting over the network to somebody who reads it, with a threshold decided and an action attached to it. It is what turns an August problem into a June email.
- Metered power distribution, so you know how much each line draws and do not discover the limit the day one more piece of equipment is plugged in.
- And the order inside: cabling labelled and routed, free space kept back, and the cabinet key controlled — because the whole security system of the building lives in there and getting to it is usually easier than getting into what the cameras watch.
Who administers it when we leave.
This is split between IT and maintenance, and it works when who does what is written down.
The monitoring is IT's: the temperature and humidity sensors and the metered distribution alert over the network, and that goes into the house alerting system like anything else. With that, a cabinet that is heating up is detected in spring.
The physical maintenance belongs to the building's maintenance team and it is not much, but it has to be done: clean or change the filters, check that the fans turn, inspect the cooling if there is any and look that nobody has left boxes in front of the air intake grille. That last one happens constantly.
Our part is the calculation when something changes: adding a server, putting in a graphics card or filling the cabinet means redoing the sum of the watts and checking that the cooling and the backup still cope. It is half an hour and it avoids finding out in August.
Where to go next.
The cabinet and the power are the same decision: what you put inside draws power, and what draws power heats up.
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Have you put your hand in your cabinet on a hot day?
If the air inside is hot and still, you already know what is going to break first. Tell us what is inside and which room it is in, and we will tell you how much heat it is generating, whether ventilating is enough and what happens in August.