Re: Increasing default value for effective_io_concurrency?

On Wed, Jul 3, 2019 at 11:42:49AM -0400, Robert Haas wrote:
> On Wed, Jul 3, 2019 at 11:24 AM Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> > Maybe. And it would probably work for the systems I used for benchmarks.
> >
> > It however assumes two things: (a) the storage system actually has
> > spindles and (b) you know how many spindles there are. Which is becoming
> > less and less safe these days - flash storage becomes pretty common, and
> > even when there are spindles they are often hidden behind the veil of
> > virtualization in a SAN, or something.
>
> Yeah, that's true.
>
> > I wonder if we might provide something like pg_test_prefetch which would
> > measure performance with different values, similarly to pg_test_fsync.
>
> That's not a bad idea, but I'm not sure if the results that we got in
> a synthetic test - presumably unloaded - would be a good guide to what
> to use in a production situation. Maybe it would; I'm just not sure.

I think it would be better than what we have now.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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