Re: O_DSYNC broken on MacOS X? - Mailing list pgsql-hackers

From A.M.
Subject Re: O_DSYNC broken on MacOS X?
Date
Msg-id 26F4C746-B594-46BC-9AB9-C5793F8425EE@themactionfaction.com
Whole thread Raw
In response to Re: O_DSYNC broken on MacOS X?  (Bruce Momjian <bruce@momjian.us>)
Responses Re: O_DSYNC broken on MacOS X?
List pgsql-hackers
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?

Cheers,
M

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