| From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
|---|---|
| To: | Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Allow a per-tablespace effective_io_concurrency setting |
| Date: | 2015-09-02 21:58:33 |
| Message-ID: | CAHyXU0zmLcqE_=e50ZyhReNGy_AcEwTCPdcOfw_BS3w5Ssa-BQ@mail.gmail.com |
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| Lists: | pgsql-hackers pgsql-performance |
On Wed, Sep 2, 2015 at 4:31 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> On 09/02/2015 02:25 PM, Tomas Vondra wrote:
>>
>> As I explained, spindles have very little to do with it - you need
>> multiple I/O requests per device, to get the benefit. Sure, the DBAs
>> should know how many spindles they have and should be able to determine
>> optimal IO depth. But we actually say this in the docs:
>
> My experience with performance tuning is that values above 3 have no
> real effect on how queries are executed.
That's the exact opposite of my findings on intel S3500 (see:
http://www.postgresql.org/message-id/CAHyXU0yiVvfQAnR9cyH=HWh1WbLRsioe=mzRJTHwtr=2azsTdQ@mail.gmail.com).
merlin
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