| From: | Evgeny Shishkin <itparanoia(at)gmail(dot)com> |
|---|---|
| To: | Claudio Freire <klaussfreire(at)gmail(dot)com> |
| Cc: | Craig James <cjames(at)emolecules(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Two identical systems, radically different performance |
| Date: | 2012-10-08 22:46:38 |
| Message-ID: | A62086F6-67AE-441F-85A5-9C26EF59EBC4@gmail.com |
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| Thread: | |
| Lists: | pgsql-performance |
On Oct 9, 2012, at 2:44 AM, Claudio Freire <klaussfreire(at)gmail(dot)com> wrote:
> 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.
This, i also suggest to rebenchmark with increased wal_buffers. May be that downscale comes from wal mutex contention.
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