Date: Fri, 20 Oct 1995 12:12:16 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: questions@freebsd.org Subject: Re: SCSI HD recommendation Message-ID: <199510200242.MAA17063@genesis.atrad.adelaide.edu.au> In-Reply-To: <199510191817.LAA02975@phaeton.artisoft.com> from "Terry Lambert" at Oct 19, 95 11:17:51 am
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Terry Lambert stands accused of saying: > > ERRR??? AV means ``Audio/Video'' (or something), and they do strange > > things (probably have a whacking great big on-board cache) so that > > when the drive auto-recalibrates it doesn't slow down any transfers > > too much, so that digital audio/video applications won't notice the > > disk going off and doing housekeeping. > > > > Hence, they are normally (at least) 5% >>MORE<< than the ordinary > > drives. > > Not all AV implementations use cache. > > Most, in fact, skip the thermal recalibration, reducing the MTBF for > the drive. > > As a matter of fact, I don't know of an AV drive that uses a cache > to prevent thermal recalibration delays instead of skipping the > recalibration entirely. Most actually just support _interrupting_ the recalibration. Not performing thermal recal at all would result in a totally unusable drive. (Consider the width of a track and the coefficient of expansion of aluminium over a 60C operating range (being conservative)) > In my experience, AV drives are less reliable, a trade-off for real-time > streaming response -- not a typical concern for your average non-AV user. I can't comment there; AV drives are still at a premium here, but a lot of "mainstream" drives seem to be offering interruptible recal as well now, so I think the difference is closing rapidly. > Terry Lambert -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] My car has "demand start" -Terry Lambert UNIX: live FreeBSD or die! [[
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