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Re: Shared buffers, db transactions commited, and write IO on Solaris

From: Erik Jones <erik(at)myemma(dot)com>
To: josh(at)agliodbs(dot)com
Cc: pgsql-performance(at)postgresql(dot)org, Dimitri <dimitrik(dot)fr(at)gmail(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: Shared buffers, db transactions commited, and write IO on Solaris
Date: 2007-03-30 04:27:06
Message-ID: 39BA9EF6-4928-4128-B4BB-A8DE2C536053@myemma.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Mar 29, 2007, at 7:23 PM, Josh Berkus wrote:

> Erik,
>
> Wow, thanks for the post.
>
> We've just started testing the option of sizing shared_buffers  
> bigger than
> the database, and using forcedirectio in benchmarks at Sun.  So  
> far, our
> experience has been *equal* performance in that configuration, so it's
> *very* interesting to see you're getting a gain.
>
> -- 
> --Josh

Josh,

You'er welcome!  However, I believe our situation is very different  
from what you're testing if I understand you correctly.  Are you  
saying that you're entire database will fit in memory?  If so, then  
these are very different situations as there is no way ours could  
ever do that.  In fact, I'm not sure that forcedirectio would really  
net you any gain in that situation as the IO service time will be  
basically nil if the filesystem cache doesn't have to page which I  
would think is why your seeing what you are.

erik jones <erik(at)myemma(dot)com>
software developer
615-296-0838
emma(r)



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