From owner-freebsd-questions@freebsd.org  Sun Apr 17 08:40:23 2016
Return-Path: <owner-freebsd-questions@freebsd.org>
Delivered-To: freebsd-questions@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id 5FF18AEE0E2
 for <freebsd-questions@mailman.ysv.freebsd.org>;
 Sun, 17 Apr 2016 08:40:23 +0000 (UTC)
 (envelope-from steve@sohara.org)
Received: from uk1mail2513.mymailbank.co.uk
 (UK1MAIL2513-PERMANET.IE.mymailbank.co.uk [217.69.47.44])
 by mx1.freebsd.org (Postfix) with ESMTP id D52B71070
 for <freebsd-questions@freebsd.org>; Sun, 17 Apr 2016 08:40:21 +0000 (UTC)
 (envelope-from steve@sohara.org)
Received: from smtp.lan.sohara.org (UnknownHost [88.151.27.41]) by
 uk1mail2513-d.mymailbank.co.uk with SMTP; 
 Sun, 17 Apr 2016 09:40:03 +0100
Received: from [192.168.63.1] (helo=steve.lan.sohara.org)
 by smtp.lan.sohara.org with smtp (Exim 4.86 (FreeBSD))
 (envelope-from <steve@sohara.org>)
 id 1ariFK-0004Dk-Gk; Sun, 17 Apr 2016 08:39:58 +0000
Date: Sun, 17 Apr 2016 09:39:57 +0100
From: Steve O'Hara-Smith <steve@sohara.org>
To: Matthias Apitz <guru@unixarea.de>
Cc: freebsd-questions@freebsd.org
Subject: Re: tool for mapping away bad blocks on an external disk
Message-Id: <20160417093957.0b1acb4c37d7c15a4b06af88@sohara.org>
In-Reply-To: <20160417072641.GA2358@c720-r292778-amd64>
References: <20160417072641.GA2358@c720-r292778-amd64>
X-Mailer: Sylpheed 3.5.0 (GTK+ 2.24.29; amd64-portbld-freebsd10.1)
X-Clacks-Overhead: "GNU Terry Pratchett"
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.21
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions/>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 17 Apr 2016 08:40:23 -0000

On Sun, 17 Apr 2016 09:26:41 +0200
Matthias Apitz <guru@unixarea.de> wrote:

> 
> Hello,
> 
> I have an older external disk, connected through USB, which has bad
> blocks:

	The tool you're looking for is badsect - I'm moderately surprised
it's still around, the last time I used it was on FreeBSD 1.1.5.1 but it is
still in FreeBSD 10.3.

	It doesn't do the analysis though - you'll have to do that with the
filesystem unmounted and just used dd conv=noerror if=<device> of=/dev/null
to read the whole device and pull the duff sectors out of the error
messages.

	However it's been a *long* time since this was worth doing except
perhaps as a last ditch data recovery exercise, drives have had internal
sector remapping for a long time now and when that stops working they are
well and truly banjaxed.

-- 
Steve O'Hara-Smith <steve@sohara.org>