Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29])
	by malur.postgresql.org with esmtp (Exim 4.72)
	(envelope-from <mark.kirkwood@catalyst.net.nz>) id 1TLMTY-0003dZ-4S
	for pgsql-performance@postgresql.org; Mon, 08 Oct 2012 23:11:04 +0000
Received: from [2404:130:0:10::40:2] (helo=mail.catalyst.net.nz)
	by magus.postgresql.org with esmtp (Exim 4.72)
	(envelope-from <mark.kirkwood@catalyst.net.nz>) id 1TLMTV-0002u1-Dy
	for pgsql-performance@postgresql.org; Mon, 08 Oct 2012 23:11:03 +0000
Received: from localhost (localhost [127.0.0.1])
	by mail.catalyst.net.nz (Postfix) with ESMTP id 9FC103289C
	for <pgsql-performance@postgresql.org>;
	Tue,  9 Oct 2012 12:10:55 +1300 (NZDT)
X-Virus-Scanned: Debian amavisd-new at catalyst.net.nz
Received: from mail.catalyst.net.nz ([127.0.0.1])
	by localhost (bertrand.catalyst.net.nz [127.0.0.1]) (amavisd-new,
	port 10024)
	with ESMTP id BjvSJSZx48Tj for <pgsql-performance@postgresql.org>;
	Tue,  9 Oct 2012 12:10:54 +1300 (NZDT)
Received: from [IPv6:2404:130:0:1000:9d99:996:b487:e074] (unknown
	[IPv6:2404:130:0:1000:9d99:996:b487:e074])
	(Authenticated sender: mark.kirkwood)
	by mail.catalyst.net.nz (Postfix) with ESMTPSA id A724532524
	for <pgsql-performance@postgresql.org>;
	Tue,  9 Oct 2012 12:10:54 +1300 (NZDT)
Message-ID: <50735D7E.7000405@catalyst.net.nz>
Date: Tue, 09 Oct 2012 12:10:54 +1300
From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
	rv:15.0) Gecko/20120912 Thunderbird/15.0.1
MIME-Version: 1.0
To: pgsql-performance@postgresql.org
Subject: Re: Two identical systems, radically different performance
References: 
 <CAFwQ8rcvw4mSoJ9q+ouONCeB9dg1T9gAUV5J27MpVZrehRHayQ@mail.gmail.com>
	<4CB0E3B6-CF1E-4B54-9900-E8356744F0AA@gmail.com>
	<CAFwQ8rd1TTLh-BfMf-Uc2Vv_8GuP2uQqWAa6-FrtmJUhy3LVxQ@mail.gmail.com>
	<CAGTBQpZnkU7n4iAhiNzN3rsMW2WT+H6YpN7c7bkNbfj+3hr6NA@mail.gmail.com>
	<CAFwQ8rfVgRXQLaHULbvpD65+7jYsAt9ANqujOwnksFLGYHkZew@mail.gmail.com>
	<CAGTBQpbFSWPR1Z9NiN_B6amhONjyt9PvoT13Z=SdPN8GoKZi2Q@mail.gmail.com>
	<CAFwQ8rdmzO046cXO-mqcsZKsj9Ch_W-mfiJpeQnOx8xob-SMVw@mail.gmail.com>
In-Reply-To: 
 <CAFwQ8rdmzO046cXO-mqcsZKsj9Ch_W-mfiJpeQnOx8xob-SMVw@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Host-Lookup-Failed: Reverse DNS lookup failed for 2404:130:0:10::40:2
	(failed)
X-Pg-Spam-Score: -1.1 (-)
X-Archive-Number: 201210/74
X-Sequence-Number: 48033

On 09/10/12 11:48, Craig James wrote:
> 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.
>

Maybe check all sysctl's are the same - in particular:

vm.zone_reclaim_mode

has a tendency to set itself to 1 on newer hardware, which will reduce 
performance of database style workloads.

Cheers

Mark