Date: Tue, 2 Apr 1996 19:52:07 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: Zeki@Dilbert.Oasysinc.com (Zeki Basbuyuk) Cc: stable@FreeBSD.ORG Subject: Re: SCSI Performance under -stable/-current Message-ID: <199604021022.TAA14221@genesis.atrad.adelaide.edu.au> In-Reply-To: <01BB2033.F2720440@seyma> from "Zeki Basbuyuk" at Apr 2, 96 00:38:28 am
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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 [[
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