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

Tom Lane wrote:
> Andreas Pflug <pgadmin@pse-consulting.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