[Neil]

I have been in an IT building for one of my previous employers.

It was really 2 buildings next to each other with an extra outer wall about 3 feet from the two buildings. From the outside it looking like one. It looked like it was military except it had no machine guns.

Inside everything was duplicated. If the main or backup mains supplies went down everything was backup up by UPS rooms.

The pair of diesel generators were kept warm using oil heaters. If the batteries failed to start the diesels then they were started using compressed air which as blown down 2 of the cylinders to turn the engines over. Big air receivers held the air in case they needed to start them this way.

It was very impressive and this was only the companies backup facility. The main facility was several miles away, they would not say where as only a handful of people know the location of both. They were not happy with the distance between them and were worried a natural (or not) disaster might take them both out. There were in the process of planning a new facility hundreds of miles away to be the backup. When the first were built the technology for fast comms over that distance was not available.