Re: SpeedComparison

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От Kenneth Marshall
Тема Re: SpeedComparison
Дата
Msg-id 20060211225048.GA447@it.is.rice.edu
обсуждение исходный текст
Ответ на Re: SpeedComparison  (Jochem van Dieten <jochemd@gmail.com>)
Ответы Re: SpeedComparison  (Tom Lane <tgl@sss.pgh.pa.us>)
Список 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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