The second data centre we visit – Karlsruhe Brauerboulevard – is in a much more urban setting, and looks more like a standard office building – albeit with some fairly comprehensive cooling on the 1,000 square metre roof and 25,000 servers in the basement.

Ever wondered where your stuff is stored?

This setup cost £15 million and boasts 11 separate computer rooms with 660 racks. It uses 8MW of power – the city it's in consumes just 361MW as a whole.

Ever wondered where your stuff is stored?

Everything is built with redundancy in mind, so there are two complete cooling systems to remove the hot air. There are eight cold water sets and 61 air circulating coolers.

Ever wondered where your stuff is stored?

Ever wondered where your stuff is stored?

Ever wondered where your stuff is stored?

If the power should fail, massive battery rooms can power the servers for up to 20 minutes.

Ever wondered where your stuff is stored?

In reality, it takes mere seconds for the diesel engines on the roof to power up and take over. As it is, the engines look virtually unused – because they are. In fact, they've only come on-stream once, two years ago, and for a very "short period of time". Five of these massive 39 tonne units also sit atop the roof.

Ever wondered where your stuff is stored?

Ever wondered where your stuff is stored?

Again, there are redundant engines on standby and, should there be a major power problem for days on end, 1&1 has arrangements with diesel fuel suppliers as a contingency. The building also has early fire detection with gas extinguishing systems so that the servers are not harmed if a small fire is detected.

The building also has incredible security. Not only are there 190 cameras, but access controls at all points and a man trap to gain access to the server rooms themselves.

Before TechRadar visited, we had to provide our weight to 1&1 so we wouldn't get caught in the mantrap.

Ever wondered where your stuff is stored?

Ever wondered where your stuff is stored?

Ever wondered where your stuff is stored?

Ever wondered where your stuff is stored?

Soon, though, these data centres will be dwarfed by a new sibling. 1&1 is also building a data centre (see below) with space for over 100,000 servers at Hanau. Work started two years ago in a building that was a nuclear fuel factory to produce mixed oxide rods from enriched uranium and plutonium, but it never became operational. It'll be huge.

Data centres

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