Date: Sun, 15 Nov 1998 12:46:39 -0700 (MST) From: "Justin T. Gibbs" <gibbs@narnia.plutotech.com> To: "Robert G. Brown" <rgb@phy.duke.edu> Cc: aic7xxx@FreeBSD.ORG Subject: Re: Drive constantly grinding ... Message-ID: <199811151946.MAA13725@narnia.plutotech.com> In-Reply-To: <Pine.LNX.3.96.981115143316.5548A-100000@ganesh.phy.duke.edu>
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In article <Pine.LNX.3.96.981115143316.5548A-100000@ganesh.phy.duke.edu> you wrote: > On Sun, 15 Nov 1998, There can be only one. wrote: >> I'll just slowly go insane ... click-click, click-click .... ;-) > > I have a drive or two that does the same thing. Never have figured out > if it was the drive or linux, but a Barracuda on a 2940 UW clicks every > five seconds on what sounds like a seek. Altering update doesn't seem > to matter. > > rgb 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. -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-aic7xxx" in the body of the message
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