From owner-freebsd-questions Sat Sep 27 03:00:40 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id DAA15146 for questions-outgoing; Sat, 27 Sep 1997 03:00:40 -0700 (PDT) Received: from gatekeeper.barcode.co.il (gatekeeper.barcode.co.il [192.116.93.17]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id DAA15138 for ; Sat, 27 Sep 1997 03:00:32 -0700 (PDT) Received: (from nadav@localhost) by gatekeeper.barcode.co.il (8.8.5/8.6.12) id LAA14951; Sat, 27 Sep 1997 11:59:09 +0200 (IST) Date: Sat, 27 Sep 1997 11:59:09 +0200 (IST) From: Nadav Eiron To: Alec Kloss cc: freebsd-questions@FreeBSD.ORG Subject: Re: Adaptec 3940UW performance with two drives In-Reply-To: <199709262104.QAA02443@d2si.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-questions@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk On Fri, 26 Sep 1997, Alec Kloss wrote: > Howdy. I have an Adaptec 3940UW controller in a machine. The 3940UW > has two SCSI busses on it. Originally, I had two Quantum XP34550W > drives on bus A and a Jaz drive and a CDROM drive on bus B. I got > sick of the Jaz drive and CDROM (I never used them anyway) so I > removed them. Is there any reason to (or not to) move one of the > Quantum's onto bus B? I suspect it is important to observe that I do > not copy data between the two drives very often. > > No. There is actually a gain in performance by splitting your I/O between the busses. If the transfers are between devices on different busses the read and write operations do not contend for bandwidth on the SCSI bus. However, I doubt it that your two disks saturate even a single bus under normal operation, so you'll probably see only small changes in performance anyhow. Nadav