Re: Massive performance issues

On Thu, Sep 01, 2005 at 11:52:45PM +0200, Steinar H. Gunderson wrote:
> On Thu, Sep 01, 2005 at 10:13:59PM +0100, Matthew Sackman wrote:
> > Well that's the thing - on the queries where it decides to use the index
> > it only reads at around 3MB/s and the CPU is maxed out, whereas when it
> > doesn't use the index, the disk is being read at 60MB/s. So when it
> > decides to use an index, I don't seem to be IO bound at all. Or at least
> > that's the way it seems to me.
>
> You are I/O bound; your disk is doing lots and lots of seeks. The SATA
> interface is not the bottleneck; the disk's ability to rotate and move its
> heads is.

Ahh of course (/me hits head against wall). Because I've /seen/ it read
at 60MB/s I was assuming that if it wasn't reading that fast then I'm
not IO bound but of course, it's not reading sequentially. That all
makes sense. Been a long day etc... ;-)

Matthew