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Re: Two identical systems, radically different performance - Mailing list pgsql-performance

From Craig James
Subject Re: Two identical systems, radically different performance
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Msg-id CAFwQ8rdmzO046cXO-mqcsZKsj9Ch_W-mfiJpeQnOx8xob-SMVw@mail.gmail.com
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In response to Re: Two identical systems, radically different performance  (Claudio Freire <klaussfreire@gmail.com>)
Responses Re: Two identical systems, radically different performance  (Claudio Freire <klaussfreire@gmail.com>)
Re: Two identical systems, radically different performance  (Mark Kirkwood <mark.kirkwood@catalyst.net.nz>)
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On Mon, Oct 8, 2012 at 3:44 PM, Claudio Freire <klaussfreire@gmail.com> wrote:
On Mon, Oct 8, 2012 at 7:25 PM, Craig James <cjames@emolecules.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.

But again ... the two systems are identical.  This can't explain it.

Thanks,
Craig

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