The sub-cranially installed neuro-net processor, that comes pre-installed at point of delivery. Upgrades are impossible (as far as I know in regard to current technology), although it's native processing potential is enourmous, and limits to it's potential have not been identified (again, as far as my knowledge of current technology goes). Basic maintenance is a breeze as this component (cannot really call it a peripheral) responds to the same upkeep process/resources as the rest of the system as a whole. Storage capacity is enourmous, specialist maintenance can be performed to enhance the component performance for this benchmark. Ultimate portability, is the biggest plus point. I thoroughly agree with apdyck's recommendation.

Raid on top of NBD works (with caveats), I tried a proof of concept once, RAID5 made out of nbd units. The configuration needs to be though through carefully so that data is striped across sufficient clients to prevent excessive resource (CPU and network) at the client end. I did it my building one PC with Linux and "mounting" each of the NBD pieces shared by the enn-user Windows PC's, then simply build RAID over the top of that. With sufficient planning you can make it quite resilient, just in case a user decides to switch off their PC. I did find that re-building the stripes when a PC did get turned off, caused the "server" (ie the Linux PC) to be heavily utilised, and this caused the clients that mounted/used the shared-out space from the "server" to receive quite poor performance. The only way I could think of really making this a serious possibility would be to beef-up the power of the "server" quite significantly and to ensure really fast network connections between it and the nbd hosting machines.