The biggest RAM database of all…

ein höchst interessanter Artikel über Google und Memory-Resident Databases im allgemeinen…besonders interessant in Hinblick auf TFSNA2.

“Orkut is wicked fast; Friendster isn’t. How do you reliably make a scalable web service wicked fast? Easy: the whole thing has to be in memory, and user requests must never wait for disk.

A disk head seek is about 9ms, and the human perceptual threshold for what seems “instant” is around 50ms. So if you have just one head seek per user request, you can support at most 5 hits/second on that server before users start to notice latency. If you have a typical filesystem with a little database on top, you may be up to 3+ seeks per hit already. Forget caching; caching helps the second user, and doesn’t work on systems with a “long tail” of zillions of seldom-accessed queries, like search.”