Re: O_DSYNC broken on MacOS X?

On Oct 19, 2010, at 11:22 AM, Bruce Momjian wrote:

> Greg Smith wrote:
>> A.M. wrote:
>>> Perhaps a simpler tool could run a basic fsyncs-per-second test and prompt the DBA to check that the numbers are within the realm of possibility.
>>> 
>> 
>> This is what the test_fsync utility that already ships with the database 
>> should be useful for.  The way Bruce changed it to report numbers in 
>> commits/second for 9.0 makes it a lot easier to use for this purpose 
>> than it used to be.  I think there's still some additional improvements 
>> that could be made there, but it's a tricky test to run accurately.  The 
> 
> test_fsync was designed to test various things like whether several
> open-sync writes are better than two write and an fsync, and whether you
> can fsync data written on a different file descriptor.  It is really a
> catch-all test right now, not one specific for choosing sync methods.

I am working on simplifying the test_fsync tool and making it a contrib function which can be run by the superuser based on the configured fsync method. That way, the list can ask a user to run it to report fsyncs-per-second for suspiciousness. The goal is to make it more accessible. I was also thinking about adding some notes along the lines of "Your drive fsync speed rates between a 5400 RPM SATA drive and a 7200 RPM SATA drive." or "Your drive fsync speed rates as high as RAM- your fsync method may be wrong."

Currently, the test tool is not even compiled by default.

Thoughts?

Cheers,
M