Thread: different io elevators in linux

I haven't read much FAQs but has anyone done some benchmarks with
different io schedulers in linux with postgresql?

Look at these:
http://kerneltrap.org/node/view/843
http://simonraven.nuit.ca/blog/archives/2004/05/20/quikconf/


Maybe its well known knowledge but i just found this information and
haven't had time to do my own testing yet.

mvh

--
Björn Bength  |  Systems Designer
--
Curalia AB  |  www.curalia.se
Tjärhovsgatan 21, SE - 116 28 Stockholm, Sweden
Phone: +46 (0)8-410 064 40
--

Bjorn,

> I haven't read much FAQs but has anyone done some benchmarks with
> different io schedulers in linux with postgresql?

According to OSDL, using the "deadline" scheduler sometimes results in a
roughly 5% boost to performance, and sometimes none, depending on the
application.   We use it for all testing, though, just in case.

--Josh

--
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco

On Mon, Oct 25, 2004 at 10:09:17AM -0700, Josh Berkus wrote:
> Bjorn,
>
> > I haven't read much FAQs but has anyone done some benchmarks with
> > different io schedulers in linux with postgresql?
>
> According to OSDL, using the "deadline" scheduler sometimes results in a
> roughly 5% boost to performance, and sometimes none, depending on the
> application.   We use it for all testing, though, just in case.
>
> --Josh
>

Yes, we found with an OLTP type workload, the as scheduler performs
about 5% worse than the deadline scheduler, where in a DSS type
workload there really isn't much difference.  The former doing a
mix of reading/writing, where the latter is doing mostly reading.

Mark