Date: Mon, 16 Nov 1998 09:40:45 -0500 (EST) From: "Robert G. Brown" <rgb@phy.duke.edu> To: "Justin T. Gibbs" <gibbs@narnia.plutotech.com> Cc: aic7xxx@FreeBSD.ORG Subject: Re: Drive constantly grinding ... Message-ID: <Pine.LNX.3.96.981116093711.5548C-100000@ganesh.phy.duke.edu> In-Reply-To: <199811151946.MAA13725@narnia.plutotech.com>
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On Sun, 15 Nov 1998, Justin T. Gibbs wrote: > What you are hearing is likely what Seagate calls 'dithering'. > When the drive is otherwise idle, the head is moved to new locations > periodically so that it doesn't pass over the same piece of media > for extended periods of time. The Seagate representative told us > (Pluto) that this was done to ensure that if a plater contained an > imperfection that caused the head to 'brush' the platter occassionally > (not a head crash) the head would not wear out the platter. For > real time applications (Pluto offers real time video editor/server > products) where you want the head to stay where you put it, this > is somewhat annoying. Pluto's work around is to send a Test Unit > Ready command to the drive every 500ms or so which restarts the > 'diterhing timer' and prevents the extra seeks. This is very interesting information. If I understand it then, this is a feature, not a bug, and will theoretically improve the lifetime and reliability of your drive. So if one can live with the per 5s whirr, (and aren't doing real time applications) the best solution is just to ignore it. This is fine with me. I really appreciate your passing the information on. I long ago decided that it was not likely to be a fatal problem, but it is very comforting to know that it isn't a problem at all but rather a deliberate design feature. rgb Robert G. Brown http://www.phy.duke.edu/~rgb/ Duke University Dept. of Physics, Box 90305 Durham, N.C. 27708-0305 Phone: 1-919-660-2567 Fax: 919-660-2525 email:rgb@phy.duke.edu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-aic7xxx" in the body of the message
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