Whirlibird,Here are the stats on the NSA Utah data center only since the NSA has other data centers.
Storage: Estimates come in around the thousands of zettabytes or yottabytes. The military has estimated, as a comparative example, that its entire network storage exceeds exabytes and possibly yottabytes.
I believe they can store all information from everyone everyday for more the five years and that is only the Utah data center, they have others.
Computer capabilities: Cray XC30 Supercomputers will serve the facility, running up to 1 million Intel Xenon core processors at the same time as fast as 100 petaflops. SLT.com described one petaflop as about one thousand trillion calculations per second. This would put the system as three times faster than the world’s fastest supercomputer.
Size: 1 million square feet. 100,000 square feet will compose four data halls with data-storage servers. 900,000 square feet will serve for technical and administrative support staff,which is expected to be less than 200 employees.
They are all connected. I think Miami data is small potatoes for the NSA, the NSA has the storage space for all data, email traffic, video, cellphone on a world wide bases to store for over five years which is a lot of data.
The servers are becoming smaller and are able to hold more data.