*BSD News Article 44265


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From: hdslip@iii1.iii.net (HD Associates)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: /sbin/badsect
Date: 19 May 1995 08:40:21 -0400
Organization: HD Associates, Inc.
Lines: 39
Message-ID: <3pi3k8$d2r@iii1.iii.net>
References: <3pggv4$1ir@case.cyberspace.com> <3pgl5j$lri@park.uvsc.edu> <3ph7fr$9u7@case.cyberspace.com>
NNTP-Posting-Host: iii1.iii.net

In article <3ph7fr$9u7@case.cyberspace.com>,
Jack Valko <valko@cyberspace.com> wrote:
>Terry Lambert (terry@cs.weber.edu) wrote:
>
>: SCSI does this for you automatically.
>
>: If you have a SCSI device (the sd0a you refer to is a SCSI drive
>: name) that has a bad sector, then it is already fixed.
>
>: If it isn't, you're drive is on the verge of going to hell in a
>: handbasket, since you must be out of replacements.
>
>I do have a SCSI drive.  Bummer.  Will a low-level reformat fix the problem?

There are two problems here:

1. SCSI drives are frequently shipped with read and write reallocation
disabled.  That was the case for all three SCSI drives I have.  To
enable them, use the new mode editing feature in
freebsd-current (AKA 2.05) to edit mode page 1 and be sure
that the A[WR]RE fields are set to 1.

(command is scsi -f /dev/rsd?c -m 1 -e -P 3)

> AWRE (Auto Write Reallocation Enbld):  1
> ARRE (Auto Read Reallocation Enbld):  1

After the feature freeze lifts I'll put a sanity check in sd.c
that will complain about misconfigured drives during boot.

2. A drive will only reallocate a read error if it can successfully
recover the data.  This means that if you can't read the data you
will have to read/ignore error/write the block, or tell the drive
to forceably reallocate the block.  I may write a disk scrub utility
that can run against an unmounted drive.
-- 
Peter Dufault               Real Time Machine Control and Simulation
HD Associates, Inc.         Voice: 508 433 6936
dufault@hda.com             Fax:   508 433 5267