Re: Two identical systems, radically different performance

On Oct 9, 2012, at 2:44 AM, 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.

This, i also suggest to rebenchmark with increased wal_buffers. May be that downscale comes from wal mutex contention.