Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!umcp-cs!chris
From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.unix-wizards,net.bugs.4bsd
Subject: Re: Possible uda50 driver problem
Message-ID: <3306@umcp-cs.UUCP>
Date: Sun, 7-Sep-86 22:07:13 EDT
Article-I.D.: umcp-cs.3306
Posted: Sun Sep  7 22:07:13 1986
Date-Received: Mon, 8-Sep-86 00:17:08 EDT
References: <189@miduet.gec-mi-at.co.uk> <3151@umcp-cs.UUCP> <194@miduet.gec-mi-at.co.uk>
Reply-To: chris@umcp-cs.UUCP (Chris Torek)
Organization: University of Maryland, Dept. of Computer Sci.
Lines: 30
Xref: mnetor net.unix-wizards:7808 net.bugs.4bsd:920

[Some of this is being taken off line.]

In article <194@miduet.gec-mi-at.co.uk> steve@gec-mi-at.co.uk
(Steve Lademann) writes:
>With regard to bad block replacement [on UDA50s] ... from what
>I've seen with regard to the bad block replacement algorithms,
>there is a lot of Black Magic involved in the process anyway.

Not really.  The idea is very straightforward: save the original
data, allocate a replacement block, test it, copy the original data
to it, and mark the original block as forwarded.  The ugliness is
all caused by state saving for error recovery---our old friend the
commit. . . .  The problem gets worse if the forwarding code is
outside the driver.  What happens if the machine crashes during
forwarding?  (If the driver does things with the block half-forwarded,
who knows what might happen.)

>What will your solution to the problem of getting rid of bad blocks be
>(if any)? I must admit that after your comments with regard to the 'iffy'
>algorithm in the RIACS driver, mine could well be to call Field Service!

Well, actually . . . yes.  At least for now.

If you have a copy of Ultrix 1.1 or later, you can run `rabads';
it is a standalone program that just forwards bad sectors.  I have
never used it myself.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1516)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@mimsy.umd.edu