Snippet: The rule is worked out like this: you calculate the break-even relative interval (RI), and if it's less than five minutes you cache the data. The form

Snippet: The rule is worked out like this: you calculate the break-even relative interval (RI), and if it's less than five minutes you cache the data. The formula is: RI = (Data pages per MB / IOPS per disk) x (price of disk / price per MB of RAM) Went looking for illustrative charts, but only found some tables in a similar 2008 piece at http://queue.acm.org/detail.cfm?id=1413264 http://queue.acm.org/detail.cfm?id=1413264 - The Five-Minute Rule 20 Years Later: and How Flash Memory Changes the Rules, by Goetz Graefe Some charts in the 1987 SIGMOD paper, http://books.google.com/books?id=7a48qSMuVcUC&pg=PA224 http://books.google.com/books?id=7a48qSMuVcUC&pg=PA224 - The Five-Minute Rule Ten Years Later, and Other Computer Storage Rules of Thumb, by Jim Gray, Goetz Graefe. With color: ftp://ftp.research.microsoft.com/pub/tr/tr-97-33.pdf