Re: Changing the default random_page_cost value

On Mon, Oct 14, 2024 at 10:20 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:

> Yeah, I think any effort to change the default value for this setting
> would require some analysis to prove that the newly proposed default
> is a more suitable setting than the current default. I mean, why 1.2 and
> not 1.1 or 1.3? Where's the evidence that 1.2 is the best value
> for this?
>

As I said, I was just throwing that 1.2 number out there. It felt right,
although perhaps a tad high (which seems right as we keep things very
conservative). I agree we should make a best effort to have an accurate,
defendable default. We all know (I hope) that 4.0 is wrong for SSDs.

> I don't think just providing evidence that random read times are closer to
> sequential read times on SSDs are closer than they are with
> HDDs is going to be enough.

...

> It would be nice to have this as a script so that other people could
> easily run it on their hardware to ensure that random_page_cost we
> choose as the new default is representative of the average hardware.

Heh, this is starting to feel like belling the cat (see
https://fablesofaesop.com/belling-the-cat.html)

Remember this is still just a default, and we should encourage people to
tweak it themselves based on their own workloads. I just want people to
start in the right neighborhood. I'll see about working on some more
research / generating a script, but help from others is more than welcome.

Cheers,
Greg