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From: Terry Lambert <terry@lambert.org>
Message-Id: <199510191817.LAA02975@phaeton.artisoft.com>
Subject: Re: SCSI HD recommendation
To: gary@palmer.demon.co.uk (Gary Palmer)
Date: Thu, 19 Oct 1995 11:17:51 -0700 (MST)
Cc: luigi@labinfo.iet.unipi.it, questions@freebsd.org
In-Reply-To: <694.814102252@palmer.demon.co.uk> from "Gary Palmer" at Oct 19, 95 12:30:52 pm
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> Luigi Rizzo stands accused of writing in message ID
> <199510191023.LAA02700@labinfo.iet.unipi.it>:
> >I have to buy a large (>= 4GB) SCSI HD, and have been offered
> >the following:
> 
> >    Fujitsu 4.3GB
> >    Micropolis 4.3GB
> >    Micropolis 4.3GB AV (?)
> >    Micropolis 9.1GB
> >    Micropolis 9.1GB AV (?)
> 
> >(don't know what the "AV" stands for, those "AV" models are about 5% cheaper
> >than the other ones).
> 
> 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.

> >Any recommendation on which of the above are known for good/bad
> >performance/reliability ?

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.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.