From owner-freebsd-stable Tue Apr 2 01:59:55 1996 Return-Path: owner-stable Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id BAA28802 for stable-outgoing; Tue, 2 Apr 1996 01:59:55 -0800 (PST) Received: from genesis.atrad.adelaide.edu.au (genesis.atrad.adelaide.edu.au [129.127.96.120]) by freefall.freebsd.org (8.7.3/8.7.3) with ESMTP id BAA28751 for ; Tue, 2 Apr 1996 01:59:15 -0800 (PST) Received: from msmith@localhost by genesis.atrad.adelaide.edu.au (8.6.12/8.6.9) id TAA14221; Tue, 2 Apr 1996 19:52:07 +0930 From: Michael Smith Message-Id: <199604021022.TAA14221@genesis.atrad.adelaide.edu.au> Subject: Re: SCSI Performance under -stable/-current To: Zeki@Dilbert.Oasysinc.com (Zeki Basbuyuk) Date: Tue, 2 Apr 1996 19:52:07 +0930 (CST) Cc: stable@FreeBSD.ORG In-Reply-To: <01BB2033.F2720440@seyma> from "Zeki Basbuyuk" at Apr 2, 96 00:38:28 am MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-stable@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk Zeki Basbuyuk stands accused of saying: > How do you get this speed? I thought there is a physical limitation > on how much speed you can get for a hard drive. The calculation is > as follows. 120 rps (revs per sec assuming 7200 rpm drive) X 40 > sectors per track (average or above average) X 512 bps (bytes per > sector) = 2.4 MB /sec. To get 6 MB either spt needs to increase to > 100 or so or rotation needs to be increased. One should always temper theory with reality. You can go a lot faster by striping your sectors across several surfaces, for example. Reality shows us that the more agressive drives will happily outrun the sustained rate your envelope calculation suggests, so I guess reality is more complicated that you're allowing for 8) > Tom -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] Collector of old Unix hardware. "Where are your PEZ?" The Tick [[