From 2005 to 2007 to 2009, the largest available hard drive grew from 500 GB to 1 TB to 2 TB. This is the normal historical trend for hard drives[1]. Projectin

From 2005 to 2007 to 2009, the largest available hard drive grew from 500 GB to 1 TB to 2 TB. This is the normal historical trend for hard drives[1]. Projecting that trend out a mere 10 years in the future, we anticipate 64 TB drives to be available, reducing requirements to 32k racks. 10 more years in the future and we have 2 PB drives, reducing requirements to a mere 1k racks. The trend of course might slow before then, but the point still stands that if you're planning on a scale of a decade or two, those numbers stop seeming impossible and start seeming inevitable. [1] http://en.wikipedia.org/wiki/History_of_hard_disk_drives#1980s_to_present_day http://en.wikipedia.org/wiki/History_of_hard_disk_drives#198...