[1939] in linux-scsi channel archive
Re: Why SCSI disks rather than IDE disks? Re: SCSI disks
daemon@ATHENA.MIT.EDU (Leonard N. Zubkoff)
Mon Jun 2 14:22:48 1997
Date: Mon, 2 Jun 1997 11:19:16 -0700
From: "Leonard N. Zubkoff" <lnz@dandelion.com>
To: welbon@bga.com
CC: linux-scsi@vger.rutgers.edu
In-reply-to: <Pine.LNX.3.96.970602122825.700I-100000@max1-36> (message from
Edward Welbon on Mon, 2 Jun 1997 12:32:59 -0500 (CDT))
Date: Mon, 2 Jun 1997 12:32:59 -0500 (CDT)
From: Edward Welbon <welbon@bga.com>
On Mon, 2 Jun 1997, Leonard N. Zubkoff wrote:
> This is certainly true, but omits the important fact that *none* of the
> highest performance disk drives are available with an IDE interface.
> All the high end disk drives also have sophisticated head motion
> optimization algorithms which can substantially improve performance when
> the drive is given multiple commands at a time to work on.
I stand corrected. I had completely fogotten about this very important
fact. I wonder if one could simulate this aspect of SCSI function with a
sufficiently intelligent IDE controller (though at that point, there would
be significantly less cost advantage to IDE).
I'd say that's very unlikely, as I doubt the IDE interface specification feeds
back enough information about the rotational position of the platter. For that
matter, all modern disks divide the disk platter radially into zones with
different numbers of sectors per track, and I doubt that information is
available either. Without it, one cannot even determine whether sector N and
sector M are on the same track. It's impossible to do optimal seek
optimization without a pretty detailed model of the disk layout and
capabilities.
Leonard
