Re: O_DSYNC broken on MacOS X?

A.M. wrote:
> 
> 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
withinthe 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
basedon 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
"Yourdrive fsync speed rates between a 5400 RPM SATA drive and a 7200 RPM SATA drive." or "Your drive fsync speed rates
ashigh as RAM- your fsync method may be wrong."
 
> 
> Currently, the test tool is not even compiled by default.
> 
> Thoughts?

Agreed.  Let me know if you have any questions.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +