Date: Mon, 10 Dec 2001 16:47:28 +1000 From: Andrew Kenneth Milton <akm@theinternet.com.au> To: "David W. Chapman Jr." <dwcjr@inethouston.net> Cc: Julian Elischer <julian@elischer.org>, Matthew Dillon <dillon@apollo.backplane.com>, Terry Lambert <tlambert2@mindspring.com>, Greg Lehey <grog@FreeBSD.ORG>, "Daniel O'Connor" <doconnor@gsoft.com.au>, sthaug@nethelp.no, freebsd-current@FreeBSD.ORG, j@uriah.heep.sax.de, joerg_wunsch@uriah.heep.sax.de Subject: Re: "Dangerously dedicated" yet again (was: cvs commit: src/sys/kern subr_diskmbr.c) Message-ID: <20011210164728.E46324@zeus.theinternet.com.au> In-Reply-To: <20011210062338.GA51934@leviathan.inethouston.net>; from David W. Chapman Jr. on Mon, Dec 10, 2001 at 12:23:38AM -0600 References: <200112100559.fBA5x2x43757@apollo.backplane.com> <Pine.BSF.4.21.0112092202050.27605-100000@InterJet.elischer.org> <20011210062338.GA51934@leviathan.inethouston.net>
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+-------[ David W. Chapman Jr. ]---------------------- | > > :> > IBM DTLA drives are known to rotate fast enough near the spindle | > > :> > that the sustained write speed exceeds the ability of the controller | > > :> > electronics to keep up, and results in crap being written to disk. | > | > | > I would adssume it actually the tracks FURTHEREST from the spindle.. | | | Wouldn't the linear speed be faster closer to the spindle at 7200 RPM | than at the edge? er no. The circumference of a circle is 2 PI r. So as your distance from the spindle increases the amount of physical real estate you're traversing increases. Since you are turning at a constant angular velocity, your linear velocity increases as the distance from the spindle increases by a factor of PI (or around 3 if you're not a maths person). Even been at one of those carnivals where they have a spinning thing? It's easier to stay near the centre, than near the edges, because you are moving a *lot* quicker at the edges. And just for the hell of it; If you have a 3 unit disc doing 1 RPM If you're 1/2 unit out you're doing ~3 units/sec If you're one unit out, you're doing ~6 units/sec If you're two units out you're doing ~12 units/sec at three; ~18 units/sec Multiply by 7200 and s/units/inches/ The outside of your disk is really moving The density of the sectors at the outer edge is lighter than near the centre, which mitigates the speed some what. See Also: artficial gravity in space stations/ships/objects -- Totally Holistic Enterprises Internet| | Andrew Milton The Internet (Aust) Pty Ltd | | ACN: 082 081 472 ABN: 83 082 081 472 | M:+61 416 022 411 | Carpe Daemon PO Box 837 Indooroopilly QLD 4068 |akm@theinternet.com.au| To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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