| From: | "Mark Woodward" <pgsql(at)mohawksoft(dot)com> |
|---|---|
| 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: | 2006-02-12 15:18:23 |
| Message-ID: | 18560.24.91.171.78.1139757503.squirrel@mail.mohawksoft.com |
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| Lists: | pgsql-hackers |
> 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.
As I have posted on this group many times, modern hard disks are very
complex beasts, it is difficult to predict what is happening on them. If
write caching is enabled, and some IDE hard disks lie as to whether or not
it is, you *never* know.
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