I wrote: > I recall that when we settled on 4.0 as a good number for > spinning-rust drives, it came out of some experimentation that > I'd done that involved multiple-day-long tests. I don't recall any > more details than that sadly, but perhaps trawling the mailing list > archives would yield useful info. It looks like the 4.0 value came > in with b1577a7c7 of 2000-02-15, so late 1999/early 2000 would be the > time frame to look in.
I tried asking https://www.postgresql.org/search/ about random_page_cost, and got nothing except search engine timeouts :-(. However, some digging in my own local archives yielded https://www.postgresql.org/message-id/flat/25387.948414692%40sss.pgh.pa.us https://www.postgresql.org/message-id/flat/14601.949786166%40sss.pgh.pa.us That confirms my recollection of multiple-day test runs, but doesn't offer much more useful detail than that :-(. What I think I did though was to create some large tables (much bigger than the RAM on the machine I had) and actually measure the runtime of seq scans versus full-table index scans, repeating plenty 'o times to try to average out the noise. There was some talk in those threads of reducing that to a publishable script, but it was never followed up on. regards, tom lane
