  Simple economic and performance arguments suggest appropriate lifetimes for
main memory pages and suggest optimal page sizes. The fundamental tradeoffs are
the prices and bandwidths of RAMs and disks. The analysis indicates that with
today's technology, five minutes is a good lifetime for randomly accessed
pages, one minute is a good lifetime for two-pass sequentially accessed pages,
and 16 KB is a good size for index pages. These rules-of-thumb change in
predictable ways as technology ratios change. They also motivate the importance
of the new Kaps, Maps, Scans, and $/Kaps, $/Maps, $/TBscan metrics.
