Date: Wed, 24 Nov 1999 23:27:49 +0100 (CET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: maex-lists-freebsd-scsi@Space.Net (Markus Stumpf) Cc: scsi@FreeBSD.ORG Subject: Re: [Q] SCSI speed and CD-ROM Message-ID: <199911242227.XAA85020@yedi.iaf.nl> In-Reply-To: <19991124194835.F95710@Space.Net> from Markus Stumpf at "Nov 24, 1999 7:48:35 pm"
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As Markus Stumpf wrote ... > On bootup I see a message > ahc0:A:4: refuses WIDE negotiation. Using 8bit transfers > > A friend of mine said that the CD-ROM slows down the SCSI bus (and thus > the disk I/O). > > Is this true > a) generally No. > b) only if the CD-ROM is active/mounted/used for I/O. > > If a) I would remove the CD-ROM, as I only use it 1 or 2 times a year > anyway and if b) I'd keep it :-))) SCSI negotiates the max speed between any 2 SCSI devices (normally the host adapter and a device). The speed of the bus is *not* the speed of the slowest device. If you had a slow-as-molasses device on your bus that one would take a looong time (compared to the fast devices) to do a data transfer. And it could get in the way (performance wise) of a faster device. A device sitting idle get's in nobody's way. Wilko -- | / o / / _ Arnhem, The Netherlands - Powered by FreeBSD - |/|/ / / /( (_) Bulte WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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