Hi, On 2025-03-18 16:22:45 -0400, Bruce Momjian wrote: > On Tue, Mar 18, 2025 at 04:13:26PM -0400, Andres Freund wrote: > > Hi, > > > > On 2025-03-18 16:08:22 -0400, Bruce Momjian wrote: > > > This commit makes our default random_page_cost = 4 out of line with > > > these new settings (assumes modern SSD/NAS/SAN hardware) and more out of > > > line with reality. > > > > How so? That seems like an independent consideration to me. > > [thread moved to hackers] > > Uh, I think our old random_page_cost and *_io_concurrency assumed > magnetic disks --- now *_io_concurrency assumes more modern hardware and > random_page_cost assumes magnetic.
The cost difference between random and non-random IO is actually still reasonably accurate with NVMEs. You can argue that random_page_cost should be 2.5, but that really depends on the specific hardware. Particularly for cloud style networked storage, you could even argue that the difference between sequential and random IO has *grow* given recent changes in PG (io combining in PG 17), as random IOs much more quickly lead to exhausting IOPS quotas. I still don't think adjusting random_page_cost has any meaningful relation to the change at hand. Greetings, Andres Freund
