From the online description of the Utah facility.
The storage capacity of the Utah Data Center will be measured in "zettabytes". What exactly is a zettabyte? There are a thousand gigabytes in a terabyte; a thousand terabytes in a petabyte; a thousand petabytes in an exabyte; and a thousand exabytes in a zettabyte. Some of our employees like to refer to them as "alottabytes".
But no machine is perfect and things do break down.