Re: fsync, fdatasync, open_sync, and open_datasync, --

Tom Lane wrote:
> Andreas Pflug <pgadmin(at)pse-consulting(dot)de> writes:
>
>>Tom Lane wrote:
>>
>>>I don't think any test that we could build would be as useful as simply
>>>trying the different settings with an installation's real workload.
>
>
>>Benchmarking the real workload isn't always so easy, and might be quite
>>time consuming to obtain meaningful values.
>
>
> The concern was about whether people might be missing an easy speedup of
> 2x or more. I don't think it'd be that hard to tell ;-) if one setting
> is an order of magnitude better than another for your workload. If
> there's not an obvious difference then you haven't wasted much effort
> checking.

This is probably more obvious with a 100 % write test app, compared to
5-10 % write as in average apps. Those 90% reading will make your
benchmarking unreliable unless you have it running for a longer period
to get a better statistic. Improving signal/noise ratio (i.e. avoiding
reads) makes it simpler.

Regards,
Andreas