Well that is quite something!
The Guardian's latest reveal in the Edward Snowden files is that they record five billion mobile phone calls, cell phones if your American, per day!
That is absolutely phenomenal! That requires and absolutely incredible amount of storage. An incredible amount!
You have to realise that this is each day and that even a single thirty minute call would be several megabytes. Depending on the quality of the call and services this could be a lot more.
I know that phone calls use a particular type of compression that is quite efficient and the quality is low. But this is likely not the case for all and audio takes a great deal of storage! Of course there could be a fair percentage of video calls too? Video would take quite a bit more storage than audio requires.
Take into account that it is rumoured to have been around ten years ago they started doing this and you need to think of a facility like that one of Woodlawn in Die Hard 4 just to house all this alone and that may be understating it some?!
NSA gathering 5bn cell phone records daily, Snowden documents show - http://www.theguardian.com/world/2013/dec/04/nsa-storing-cell-phone-records-daily-snowden?utm_medium=referral&utm_source=pulsenews