Re: Two identical systems, radically different performance

From: Claudio Freire <klaussfreire(at)gmail(dot)com>
To: Craig James <cjames(at)emolecules(dot)com>
Cc: Evgeny Shishkin <itparanoia(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Two identical systems, radically different performance
Date: 2012-10-08 22:44:04
Message-ID: CAGTBQpbFSWPR1Z9NiN_B6amhONjyt9PvoT13Z=SdPN8GoKZi2Q@mail.gmail.com
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On Mon, Oct 8, 2012 at 7:25 PM, Craig James <cjames(at)emolecules(dot)com> wrote:
>> > But why? What have I overlooked?
>>
>> Do you have readahead properly set up on the new one?
>
>
> # blockdev --getra /dev/sdb1
> 256

It's probably this. 256 is way too low to saturate your I/O system.
Pump it up. I've found 8192 works nice for a system I have, 32000 I
guess could work too.

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