Date: Thu, 23 Nov 2006 13:09:54 -0500 (EST)
From: Greg Smith <gsmith@gregsmith.com>
To: pgsql-performance@postgresql.org
Subject: Re: Direct I/O issues 
In-Reply-To: <14171.1164300342@sss.pgh.pa.us>
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References: <Pine.GSO.4.64.0611230013550.26031@westnet.com>
	<14171.1164300342@sss.pgh.pa.us>
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On Thu, 23 Nov 2006, Tom Lane wrote:

> * It does not check for errors (if it had, you might have realized the
>  other problem).

All the test_fsync code needs to check for errors better; there have been 
multiple occasions where I've run that with quesiontable input and it 
didn't complain, it just happily ran and reported times that were almost 
0.

Thanks for the note about alignment, I had seen something about that in 
the xlog.c but wasn't sure if that was important in this case.

It's very important to the project I'm working on that I get this cleared 
up, and I think I'm in a good position to fix it myself now.  I just 
wanted to report the issue and get some initial feedback on what's wrong. 
I'll try to rewrite that code with an eye toward the "Determine optimal 
fdatasync/fsync, O_SYNC/O_DSYNC options" to-do item, which is what I'd 
really like to have.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD