As of 2010, no system has yet achieved one yottabyte of storage. In fact, the combined space of all the computer hard drives in the entire world does not amount to even one yottabyte.
According to one study, all the world's computers stored approximately 160 exabytes [exabyte = 1 billion gigabytes] The yottabyte (derived from the SI prefix yotta-) is a unit of information or computer storage equal to one septillion (one long scale quadrillion or 1024) bytes (one quadrillion gigabytes). The unit symbol for the yottabyte is YB.
In Utah, the National Security Agency is building a $2 billion storage facility that will house and analyze all forms of electronic communication...a potential yottabyte of everyone's (formerly) personal data. So how big is a yottabyte? CrunchGear puts it well:
There are a thousand gigabytes in a terabyte, a thousand terabytes in a petabyte, a thousand petabytes in an exabyte, a thousand exabytes in a zettabyte, and a thousand zettabytes in a yottabyte.
In other words, a yottabyte is 1,000,000,000,000,000GB. At 487bn gigabytes (GB), if the world's rapidly expanding digital content were printed and bound into books it would form a stack that would stretch from Earth to Pluto 10 times.