"Connor McDonald" <connor_mcdonald_at_yahoo.com> wrote in message
news:3FF15551.5420_at_yahoo.com...
> Geomancer wrote:
> >
> > > well they do until you saturate it (30 mins after boot :( ).
> >
> > If I have a 4-gig cacje on top of a 100 gig EMC array, then I only get
> > 4% caching, right?
> >
> > I still find it hard to beleive that a logical I/O is only 10x-100x
> > faster than a disk read.
>
> Its easy enough to test...the hit ratio generator on my site is easily
> modified to do a timing test. The key thing is that an Oracle logical
> I/O is a lot more complex than a "read from memory".
>
> JL has conjectured that you can get approx 10,000 LIO's per sec per
> 100Mhz of CPU.
>
> hth
> connor
And bear in mind that this is one test that really should be done on the
production system or test if it is a true mirror of the live environment.
Laptops tend to have fast CPUs and slow disk systems thus skewing the
results somewhat.
--
Niall Litchfield
Oracle DBA
Audit Commission UK
Received on Tue Dec 30 2003 - 05:59:41 CST
