From: | "A(dot)M(dot)" <agentm(at)themactionfaction(dot)com> |
---|---|
To: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: O_DSYNC broken on MacOS X? |
Date: | 2010-10-19 15:38:25 |
Message-ID: | 26F4C746-B594-46BC-9AB9-C5793F8425EE@themactionfaction.com |
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Lists: | 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 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
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