Date: Mon, 16 Nov 1998 13:46:36 -0600 From: "Gary E. Bickford" <garyb@sugar-land.oilfield.slb.com> To: "Justin T. Gibbs" <gibbs@narnia.plutotech.com>, "Robert G. Brown" <rgb@phy.duke.edu> Cc: aic7xxx@FreeBSD.ORG Subject: Re: Drive constantly grinding ... Message-ID: <v04011702b276312ffdaf@[163.185.167.195]> In-Reply-To: <199811151946.MAA13725@narnia.plutotech.com> References: <Pine.LNX.3.96.981115143316.5548A-100000@ganesh.phy.duke.edu>
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At 1:46 PM -0600 11/15/98, 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. Cheetahs have a number of different usage profiles that you can set, ie for general systems use, video streaming, etc. I wonder if just setting the profile to the video streaming mode would fix that. I've never done it, just read about it. Gary E. Bickford, garyb@slb.com Sr. Systems Administrator, Connect Schlumberger http://www.connect.slb.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-aic7xxx" in the body of the message
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