Flushing disk cache for performance benchmarks?

Posted by Ido Hadanny on Server Fault See other posts from Server Fault or by Ido Hadanny
Published on 2011-06-26T15:17:31Z Indexed on 2011/06/26 16:23 UTC
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Performance

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database

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storage

I'm doing some performance benchmark on some heavy SQL script running on postgres 8.4 on a ubuntu box (natty).

I'm experiencing some pretty un-stable performance, even though I'm supposed to be the only one running on the machine (the same script on the exact same data might run in 20m and then 40m for no specific reason).

So, remembering my distant DBA training, I decided I should flush the postgres cache, using sudo /etc/init.d/postgresql restart, but it's still shaky!

My question: maybe I'm missing some caches in my disk/os? I'm using a netapp appliance as my storage. Am I on the right track? Do I even want to make sure I get repeatable performance before I start tuning?

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