Brewster Kahle is the engineering genius behind the Internet Archive, which is kind of like the NSA for the public Web. The NSA data center will accumulate private interactions and information and make them searchable; the Internet Archive’s Wayback Machine does the same thing for the open Web for historical purposes. Kahle estimates that a space of that size could hold 10,000 racks of servers (assuming each rack takes up 10 square feet). “One of these racks cost about $100,000,” says Kahle. “So we are talking $1 billion in machines.”

Kahle estimates each rack would be capable of storing 1.2 petabytes of data. Kahle says that voice recordings of all the phone calls made in the U.S. in a year would take up about 272 petabytes, or just over 200 of those 10,000 racks.

If Kahle’s estimations and assumptions are correct, the facility could hold up to 12,000 petabytes, or 12 exabytes – which is a lot of information(!) – but is not of the scale previously reported. Previous estimates would allow the data center to easily hold hypothetical 24-hour video and audio recordings of every person in the United States for a full year. The data center’s capacity as calculated by Kahle would only allow the NSA to create Beyonce-style archives for the 13 million people living in the Los Angeles metro area.

Even that reduced number struck Internet infrastructure expert Paul Vixie as high given the space allocated for data in the facility. He came up with a lower estimation. Assuming larger 13 square feet racks would be used, factoring in space between the racks, and assuming a lower amount of data storage per rack, he came up with an estimate of less than 3 exabytes of data capacity for the facility. That would only allow for 24-hour recordings of what every one of Philadelphia’s 1.5 million residents was up to for a year. Still, he says that’s a lot of data pointing to a 2009 article about Google planning multiple data centers for a single exabyte of info.