| From: | Kenneth Marshall <ktm(at)it(dot)is(dot)rice(dot)edu> |
|---|---|
| To: | Jochem van Dieten <jochemd(at)gmail(dot)com> |
| Cc: | Andrej Ricnik-Bay <andrej(dot)groups(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: SpeedComparison |
| Date: | 2006-02-11 22:50:48 |
| Message-ID: | 20060211225048.GA447@it.is.rice.edu |
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| Lists: | pgsql-hackers |
On Sat, Feb 11, 2006 at 09:21:43PM +0100, Jochem van Dieten wrote:
> On 2/11/06, Andrej Ricnik-Bay wrote:
> > Has anyone here seen this one before? Do the values
> > appear realistic?
> >
> > http://www.sqlite.org/cvstrac/wiki?p=SpeedComparison
>
> The values appear to originate from an intrsinsically flawed test setup.
>
> Just take the first test. The database has to do 1000 commits. That
> means 1000 I/O operations. There is no way that a 7200 RPM disk can do
> that in the time that that test says it took. It is reasonable to say
> that a disk can do 1 I/O operation per rotation, which means that any
> test result below 9 seconds is untrustworthy.
>
> Jochem
>
Jochem,
If the heads of the disk are in the right location, you could easily do
more than 1 commit per disk revolution so the values over 2 seconds could
actually be valid. 9 seconds would be worst case of 1 commit per revolution.
Ken
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