Disk performance (Was: How to make a REALLY FAST db server?)

On 15 Sep 2001, Gunnar Rønning wrote:

> * Ian Linwood <ian@dinwoodi.plus.com> wrote:
> |
> | I'd recommend Solaris, which has MUCH more mature MP support!
> | Linux still has a way to go (although it's getting there very
> | quickly).
>
> Maybe the Solaris MP support is more mature, I haven't tested.
> But I did some performance tests with PostgreSQL 7.0.x a little
> more than a year ago. The test were replay of real life usage of our
> web applications.
>
> The platforms were :
>
> Solaris Sparc E220r? (450 MHz cpu, 1 gig ram, 10000 rpm disks)
> Solaris Intel 750 Mhz, 256 MB ram, 7200 rpm disk.
> Linux Intel(my laptop), 466 Mhz, 128 MB ram, don't know the speed of the disks.
>
> My laptop had no problem outpeforming the others by a factor of 2.
>
> On a big batchimport, I first tested on my laptop and it took like 15-20
> minutes. The same import uses approximately 4 hours on our production box(the
> Solaris Sparc...)
A "me too" was posted under subject "Sparc seems very slow" some weeks
ago.  I did some hd-performance tests using dd and found out that while
the plain
     dd if=big-file-in of=big-file-out
shows a relation

    PC/Linux   :     Sparc/Solaris    :    Sparc/Linux
      51s                191s                 99s

an additional bs=1024k changed this relation to

    PC/Linux   :     Sparc/Solaris    :    Sparc/Linux
      61s                 45s                 35s

(which makes the choice of Linux for this particular test of dd which
is surely no SMP-test the best).  So adjusting the read/write buffer
size could be the reason for the performance problems in the beginning.
Anyway I have no idea how to tune the thing for real applications like
PostgreSQL.

Any hints?

Kind regards

         Andreas.