From owner-freebsd-questions Thu Nov 4 10:20:26 1999 Delivered-To: freebsd-questions@freebsd.org Received: from monsoon.mail.pipex.net (monsoon.mail.pipex.net [158.43.128.69]) by hub.freebsd.org (Postfix) with SMTP id 9D97B14DF6 for ; Thu, 4 Nov 1999 10:20:09 -0800 (PST) (envelope-from mark@dogma.freebsd-uk.eu.org) Received: (qmail 25078 invoked from network); 4 Nov 1999 18:20:02 -0000 Received: from useraa85.uk.uudial.com (HELO marder-1.) (62.188.130.85) by smtp.dial.pipex.com with SMTP; 4 Nov 1999 18:20:02 -0000 Received: (from mark@localhost) by marder-1. (8.9.3/8.8.8) id SAA00762; Thu, 4 Nov 1999 18:19:53 GMT (envelope-from mark) Date: Thu, 4 Nov 1999 18:19:52 +0000 From: Mark Ovens To: Marc Wandschneider Cc: "'Colin Campbell'" , questions@freebsd.org Subject: Re: SCSI v IDE Message-ID: <19991104181952.A318@marder-1> References: <13D5F9EDFD72D211BC3100105A1C2233054956@akira.lanfear.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0pre2i In-Reply-To: <13D5F9EDFD72D211BC3100105A1C2233054956@akira.lanfear.com> Organization: Total lack of Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Wed, Nov 03, 1999 at 05:31:15PM -0800, Marc Wandschneider wrote: > > > > -----Original Message----- > > From: Colin Campbell [mailto:sgcccdc@citec.qld.gov.au] > > Subject: SCSI v IDE > > > > > I have read in many places that SCSI is "better" (due to the > > ability of > > the controller to issue multiple commands to the disks). But > > if I have two > > IDEs, each on its own controller is there any real performance benefit > > with SCSI, assuming the disks are similar in performance > > characteristics? > > > SCSI disks still tend to be faster on spin speeds and access > times. up to 10k for SCSI vs like 7200 for IDES (and I still think that > most of the latter are 5400) > > As far as I'm aware, the UDMA and all that jazz that IDE drives > do still isn't as good as what SCSI does -- ie. you're still going to > get better multitasking, especially on an Un*x operating system out of a > SCSI disk. > The big advantage SCSI has over IDE is that the hardware is intelligent and so works with much less CPU overhead than IDE. It just gets on with the job of shifting data and leaves the CPU free to do other things. That is one of the main reason SCSI is more expensive than IDE. One good real world ways to see the difference between IDE and SCSI is copying large amounts of data from a CD-ROM to disk under Windows. Even with NT (which is supposed to be multi-tasking) if you start copying a large volume of data from IDE CD -> HD and watch the CPU usage meter in Task Manager it will run way high with IDE and hardly anything with SCSI. On my machine (K6-233, 64MB) it was ~95% and that slowed everything else down to a crawl, clicking in a partly hidden window would result in several seconds wait as first nothing happened, then the window outline was drawn, and finally the window contents. When I changed to all-SCSI the CPU utilization dropped to ~5% and the window raising happens almost immediately, practically as fast as normal. > of course, my knowledge might be way out of whack here .... > > marc. > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message -- STATE-OF-THE-ART: Any computer you can't afford. OBSOLETE: Any computer you own. ________________________________________________________________ FreeBSD - The Power To Serve http://www.freebsd.org My Webpage http://ukug.uk.freebsd.org/~mark/ mailto:mark@ukug.uk.freebsd.org http://www.radan.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message