>
> On Tue, 26 Dec 2000, Felix von Leitner wrote:
> > Thus spake Rik van Riel (riel@conectiva.com.br):
> > > > One more detail: top says the CPU is 50% system when reading from either
> > > > one of the disk or raid devices. That seems awfully high considering
> > > > that the Promise controller claims to do UDMA.
> > > >
> > > > Any comments?
> > > Your program reads in data at 30MB/second, on a memory bus
> > > that most likely supports something like 60 to 100MB/second.
> >
> > 100.
>
> So that's 30% for the UDMA controller and maybe
> 30% for the CPU (if your program reads in all the
> data).
Where are you getting 100MB/s?
The PCI bus can move around 130MB/sec, but RAM is lots faster.
A single PC100 DIMM can move 800MB/sec.
This P100 laptop I'm typing on gets better than 100MB/s ram reads.
Anyway, in clarification, Rik mentioned that two reads from different
disk (arrays?) on the same controller at the same time get more or less
the same speed.
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