On top of processing power, the each server has 160GB of DRAM to provide the full machine with almost 15TB of memory.

On the backend of the computer is IBM's SONAS General Parallel File System (GPFS). SONAS, or Scale-Out NAS, is a Linux-based clustered file system that almost exactly one year ago.

The clustered storage model provides massive throughput because of an increased port count that comes from cobbling many storage servers together into a single pool of disks and processors all working on a similar task and all able to share the same data through a single global name space. In other words, all of the disk drives appear as one big pool of storage capacity from which Watson can draw.

Watson's SONAS is populated with 48 450GB serial ATA (SATA) hard drives for a total of 21.61TB of capacity in a RAID 1 (mirrored) configuration; that leaves 10.8TB of raw data that is used by Watson every time it's booted up. Three terabytes of that, however, is used for the operating system and applications.

But it's not SONAS's disk-based storage that makes Watson so darned fast; it's the CPUs and memory. Every time Watson boots, the 10.8TB of data is automatically loaded into Watson's 15TB of RAM, and of that, only about 1TB is scanned for use in answering Jeopardy questions, Pearson said.