Google runs its systems on cheap, no-name IU and 2U servers -- so cheap that Google refers to them as PCs. After all each one has a standard x86 PC processor, standard IDE hard disk, and standard PC reliability - which means it is expected to fail once in three years. On a PC at home, that is acceptable for many people (if only because they're used to it), but on the scale that Google works at it becomes a real issue; in a cluster of 1,000 PCs you would expect, on average, one to fail every day. "On our scale you cannot deal with this failure by hand," said Hölzle. "We wrote our software to assume that the components will fail and we can just work around it. This software is what makes it work. [ZDNet UK]