3 ms·
Something tells me that the inclusion of an HDD into the data set would have altered the interpretation of the data. Given that it’s 30 for SSD and higher for r
by vlovich123 8mo ago
Something tells me that the inclusion of an HDD into the data set would have altered the interpretation of the data. Given that it’s 30 for SSD and higher for remote disk, it sounds like the default of 4 is either wrong or the “what is the right value for SSD “ isn’t measured correctly
- pgaddict 8mo agoGood idea. It's an interesting historical question - when we picked 4.0 as the default ~25 years ago, how close was is to the calculated value? I was asking that myself. Unfortunately I don't have a machine with traditional HDD in my homelab anymore, but I'll see if I can run the test somewhere. I wouldn't be all that surprised if this was (partially) due to Postgres being less optimized back then, which might have hidden some of the random vs. sequential differences. But that's just a wild guess.
- vlovich123 8mo agoBut also if it was calculated 25 years ago, was it the same metric you’re using today?
- pgaddict 8mo agoTo the best of my knowledge, yes. Unfortunately the details of how it was calculated in ~2000 seem to be lost, but the person who did that described he did it like this. It's possible we forgot some important details, of course, but the intent was to use the same formula. Which is why I carefully described and published the scripts, so that other engineers can point out thinkos and suggest changes.