Date: Sat, 13 Apr 1996 16:04:34 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: Brett_Glass@ccgate.infoworld.com (Brett Glass) Cc: msmith@atrad.adelaide.edu.au, jacs@gnome.co.uk, hardware@FreeBSD.ORG Subject: Re: Micropolis 1991 AV 9GB Drive Message-ID: <199604130634.QAA09620@genesis.atrad.adelaide.edu.au> In-Reply-To: <9603128293.AA829326577@ccgate.infoworld.com> from "Brett Glass" at Apr 12, 96 08:20:02 am
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Brett Glass stands accused of saying: > > > Bear in mind that both these units are _slow_, > > Average access times are supposed to be 11 ms. The fastest commonly > available drives are 8 ms, and the latest PC IDE drives sit at 12 ms or so. > Also, the 9 GB drives have huge amounts of data per cylinder and fast > spindle speeds. Why would they be slow? "Average access times" are a bit of a furphy. Look at the 'full stroke' timings for starters. IDE disks are available with better "average access times" and 12 too. The problem with these disks is that ehy have a lot of platters, and thus large actuators. Large actuators are _heavy_, and slinging them around takes more power, and more time. > > and require specialised cooling to avoid thermal overload and premature > > death, > > I've never cooled one of these in any special way. Most dissipate less > power than the 40 MB Seagates I was using 10 years ago. What experiences > have you had to indicate that they need better cooling? 1991's that die after <6months use in news servers. Trying to handle such units removed from systems that have just been powered down 8) The 40M seagate you were using 10 years ago would have been working at less than 10% duty cycle, tops. Most of the power dissipation in a disk of this type is from the actuator servo and drivers, and these disks are typically used in applications where they get worked _hard_. (News spool, large FTP servers, webcaches) > > as well as a _serious_ power supply. A normal PC chassis is > > _totally_ inappropriate for these disks. > > I am now working on a review of several such disks, packaged in external > SCSI boxes for the Macintosh. None had anywhere near as big a power supply > as your typical tower case (250-300W). J. Random Tower's PSU will have most of it's balls behind the 5V rail. Locked rotor current for these drives (ie. at startup when they're winding up), and peak impulse current (hurling the actuator around) are both drawn from the 12V rail. You need a PSU designed for disks, _particularly_ if you're not sequencing startup of more than one. I have a disk tray here with a 400W supply (designed for disks), and you can hear it popping away in current limit spinning up four of the old Seagate Wren-VII disks. These guys are rated at 35W, about the same as the 1991 and the 9G Seagates. > If you've had speed problems with these drives, or have had them overheat, > I'd like to know about it -- it'd be worth trying to verify this > information. It sounds like you're looking at them in the context of Multimedia applications, and under those circumstances these issues aren't so significant. For all the bulk data throughput, MM apps don't actually work the disk very hard. > --Brett -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] Collector of old Unix hardware. "Where are your PEZ?" The Tick [[
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