| From: | Gregory Stark <stark(at)enterprisedb(dot)com> |
|---|---|
| To: | Michael Renner <michael(dot)renner(at)amd(dot)co(dot)at> |
| Cc: | Postgres <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: How is random_page_cost=4 ok? |
| Date: | 2008-10-10 13:46:51 |
| Message-ID: | 87vdw01s1g.fsf@oxford.xeocode.com |
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| Lists: | pgsql-hackers |
Gregory Stark <stark(at)enterprisedb(dot)com> writes:
>> For "Server Drives" 3-4ms are more realistic ([2], [3]) for average seeks and
>> the 110-170MB/sec are highly exaggerated.
>
> In that case both of those numbers come straight from Seagate's data sheet for
> their top-of-the-line data centre drives:
>
> http://www.seagate.com/docs/pdf/datasheet/disc/ds_cheetah_15k_6.pdf
Oh, but I just noticed they separately quote latency and read/write seek time.
The average read seek time is 3.4ms. That gives a random_page_cost of 45-71.
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's PostGIS support!
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