10 June 2010

The Data Center: A Writer's Perspective (Part II)

Part II: The Heart of the Data Center

This is where all the servers are. My top-notch data center is built as a building within a building—both of them brick, several feet thick. The data center proper is on the bottom floor, below ground level. It would take a nearby nuclear detonation to harm the servers. After keying through another man-trap door system that separates the outer building from the inner one, you’re met by a technician who will show you to, and unlock, your company’s server rack.

Noise: The first thing you notice, upon entering, is the noise level. There are hundreds (or thousands) of servers and other equipment, all with humming power supplies and whirring fans, not to mention the whooshing of the air conditioning system. All of this combines into a constant white noise between 70 and 80 dB (a little quieter than a lawnmower [90 dB] but louder than a normal conversation [60 dB]). Contrary to what you might think, there is no beeping. Servers don’t beep as a matter of course, unless there is something very wrong.

Temperature: The next thing you notice is the temperature. Theoretically, it should be pretty cool (below 70°F) in a data center, but depending on the efficiency of the air-conditioning and the amount of equipment packed in there, it could get pretty warm.

The Plenum: The data center floor is generally one large room, although it could be subdivided into smaller spaces, and most contain caged-off areas for companies who rent multiple server cabinets. A server cabinet is a box (usually black), about 7 feet high, by 20 inches wide, by 2.5 feet deep. It has locking doors on the front and the back; usually these are perforated to allow air-flow. On the data center floor, server cabinets are arranged side-by-side in long rows. The effect is similar to a convenience store with narrow aisles and tall shelves.

The floor of most data centers is raised to allow for cables to run beneath. The floor is very solid, but consists of 2-foot-square steel or aluminum tiles (usually with a white linoleum surface coating). Any of the tiles can be lifted away by using a tool that looks like a handle attached to two suction cups. The plenum (the space between the raised floor and the sub-floor) is usually around three feet in height, though it could be as low as 1 foot. The larger the data center, the higher the raised flooring. (This is due to the fact that the chilled air is circulated in through the plenum.)

The plenum in a top-notch data center will be mostly empty (and clean). Cables will be run in neat chases, leaving plenty of room for the air to circulate (or someone to crawl around). I have seen a private data center, however, where it looked like someone dumped a giant’s pot of spaghetti down there.

Lower-end data centers might not have raised flooring. In this case, cables will be run in chases overhead.
The technicians who monitor everything work mainly in a Network Operation Center (NOC). This is a separate room—usually looking out onto the data center floor, with computers and monitors. It’s much quieter in there.

Now What?: If you’re there for legitimate purposes, you do your thing and then leave. Assuming a criminal gained entry into a data center and onto the floor, what could he do? Well, not much. First of all, there are (or should be) cameras covering the data center floor. Unless a big company is bringing in a lot of new equipment, there are generally less than three or four non-employees in the building at any given time. Guards or techs would notice someone in an area where no one is supposed to be. Remember, the lights never go out. It’s always someone’s workday in the data center.

The server cabinets are locked, and some are even surrounded by metal cages. Granted, the locks are not particularly secure, but, again, someone would notice a person trying to pick the lock of a server cabinet.

The best place a criminal could get would be into the plenum, beneath the raised floor. From here, they would have access to the entire data center. The bottoms of server cabinets are open. It is conceivable that someone could drill or cut up through the floor tile, and into a server cabinet. From there, they might be able to access network cables, network ports on servers and switches, or keyboard/monitor/mouse ports on servers. Generally, the equipment is in there pretty tight though, so access to anything but the bottom-most piece of equipment would be difficult at best. Also, don’t think about stealing equipment that way. Everything is screwed into vertical rails, and there’s no way to unscrew it without opening up the doors.

This ends our tour of the data center. To get out, please go to the lobby and return your keycard to the guard. He probably won’t be the same guard you checked in with, and he won’t ask for any ID.

If you have any questions, please wait until we’re off the datacenter floor, so we don’t have to shout.
Have your own data center experiences that differ from mine? Feel free to share.


  1. Hi Paul,

    Interesting to compare notes. The building where I work is mostly offices, but has a large datacentre in the basement.

    A lot of the things you describe are very similar to what I remember from my one visit to the datacentre itself, but there are some obvious differences.

    Because this is an active office building, there is constant traffic to & fro so the guards are actually quite busy. You need a card to get through the (single) glass doors into the atrium area, and then to any of the office corridors.

    The loading dock is not somewhere you can expect to just stroll in unnoticed. It is constantly staffed and monitored.

    The basement is quite deep down, and has a raised floor (and CCTV coverage). To get into the datacentre proper you use your card to get through a floor-to-ceiling turnstile. You need your card to get out again (through another turnstile) so the security system can clock entry & exit. There is no passing the card back through the bars to let an unauthorised accomplice in!

    You are spot on with the noise and the temperature. No beeping, and definitely no whirring tape decks!

    Other small details, if anyone wants to write about a datacentre with some authentic detail (and this may not apply to all datacentres of course):

    Ours has the rows of server cabinets arranged in alternating "hot" and "cold" aisles. Cold air comes up through the floor in one aisle, into the front of the cabinets, and hot air blows out the back of that row and gets sucked up by the ceiling vents.

    The rest of the building is heated by waste heat from the basement.

    The whole look of the place is more industrial than high-tech, with bare metal racks everywhere, bare floors, very utilitarian. Not at all like the plush & polished computer rooms in some movies.

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