The Five-Minute Rule Ten Years Later, and Other Computer Storage Rules of Thumb

TL;DR

This paper revisits and refines the 'five-minute rule' for main memory page lifetimes and other storage heuristics, based on economic and performance tradeoffs influenced by current technology parameters.

Contribution

It updates classic storage rules-of-thumb using current technology data, providing practical guidelines for memory and disk management.

Findings

Five-minute lifetime for random memory pages

One-minute lifetime for sequential pages

16 KB size for index pages

Abstract

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.