> -----Original Message-----
> From: Michael Robinton [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, May 04, 2000 10:31 PM
> To: Christopher E. Brown
> Cc: Chris Mauritz; bug1; [EMAIL PROTECTED]
> Subject: Re: performance limitations of linux raid
>
> On Thu, 4 May 2000, Christopher E. Brown wrote:
>
> > On Wed, 3 May 2000, Michael Robinton wrote:
> >
> > > The primary limitation is probably the rotational speed
> of the disks and
> > > how fast you can rip data off the drives. For instance,
> the big IBM
> > > drives (20 - 40 gigs) have a limitation of about 27mbs
> for both the 7200
> > > and 10k rpm models. The Drives to come will have to make
> trade-offs
> > > between density and speed, as the technology's in the
> works have upper
> > > constraints on one or the other. So... given enough
> controllers (either
> > > scsii on disk or ide individual) the limit will be related to the
> > > bandwidth of the disk interface rather than the speed of
> the processor
> > > it's talking too.
> >
> > Not entirely, there is a fair bit more CPU overhead running an
> > IDE bus than a proper SCSI one.
>
> A "fair" bit on a 500mhz+ processor is really negligible.
Not if you've got 12 IDE channels, with 1 drive each in a couple of big RAID
arrays. Even if all of those were mirrors (since that takes the least host
CPU RAID wise), that would suck up a lot more host CPU processing power than
the 3 SCSI channels that you'd need to get 12 drives and avoid bus
saturation.
Greg
