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Date:      Mon, 25 Nov 1996 20:12:38 -0700 (MST)
From:      Terry Lambert <terry@lambert.org>
To:        msmith@atrad.adelaide.edu.au (Michael Smith)
Cc:        terry@lambert.org, joelh@gnu.ai.mit.edu, chat@freebsd.org
Subject:   Re: A/V drives
Message-ID:  <199611260312.UAA23966@phaeton.artisoft.com>
In-Reply-To: <199611260207.MAA00521@genesis.atrad.adelaide.edu.au> from "Michael Smith" at Nov 26, 96 12:37:52 pm

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> But you're still failing to accept the basic point; A/V drives _do_
> perform thermal recal, as it is essential to maintaining drive
> performance.  However, the recal process can be preempted by incoming
> data transactions.  

So is it being done while it has been preempted?  Or does preempted
have some new meaning I'm unfamiliar with?

Look, I know that the seek performance will fall off it it fails to
recal., and I know that it will have to find it's ass with both hands
(potentially using the guard tracks to do so).  And I know that
increased head hysteresis will shorten the average time to failure,
as the AV drive, having preempted its recal, may end up being a bit
more off than a drive that completed recal without preemption.

> Ever wondered why the performance figures for A/V drives are 
> slightly different from those for the "non A/V" version in some
> cases? 

No.  One of my major claims was that they had better performance for
streaming data (if you read the start of this thread at all), and that
they made some tradeoffs to get it.  I personally consider some of the
tradeoffs to be "iffy".


> Stick to filesystems.

Natch.  And place them on drives...


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



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