From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <dgrowleyml@gmail.com>
cc: Greg Sabino Mullane <htamfids@gmail.com>,
        =?UTF-8?Q?Dagfinn_Ilmari_Manns=C3=A5ker?= <ilmari@ilmari.org>,
        pgsql-hackers <pgsql-hackers@postgresql.org>,
        Bruce Momjian <bruce@momjian.us>
Subject: Re: Changing the default random_page_cost value
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Comments: In-reply-to David Rowley <dgrowleyml@gmail.com>
	message dated "Tue, 15 Oct 2024 15:20:31 +1300"
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Date: Mon, 14 Oct 2024 22:38:01 -0400
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David Rowley <dgrowleyml@gmail.com> writes:
> 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?

Yeah, that's been my main concern about this proposal too.

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.

			regards, tom lane