From owner-freebsd-questions@FreeBSD.ORG Fri Jan 21 14:51:07 2005 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 739F316A4CE for ; Fri, 21 Jan 2005 14:51:07 +0000 (GMT) Received: from mail.scls.lib.wi.us (mail.scls.lib.wi.us [198.150.40.25]) by mx1.FreeBSD.org (Postfix) with ESMTP id 1494543D41 for ; Fri, 21 Jan 2005 14:51:07 +0000 (GMT) (envelope-from nalists@scls.lib.wi.us) Received: from [172.26.2.238] ([172.26.2.238]) by mail.scls.lib.wi.us (8.12.9p2/8.12.9) with ESMTP id j0LEoutB058059; Fri, 21 Jan 2005 08:51:02 -0600 (CST) (envelope-from nalists@scls.lib.wi.us) Message-ID: <41F116C2.40008@scls.lib.wi.us> Date: Fri, 21 Jan 2005 08:50:42 -0600 From: Greg Barniskis User-Agent: Mozilla Thunderbird 1.0 (Windows/20041206) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Ian Moore References: <200501200929.j0K9TXbl022106@mp.cs.niu.edu> <20050120151005.GA99300@gravitas.thebunker.net> <1792034180.20050120161719@wanadoo.fr> <200501220027.11740.imoore@picknowl.com.au> In-Reply-To: <200501220027.11740.imoore@picknowl.com.au> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit cc: freebsd-questions@freebsd.org cc: Anthony Atkielski Subject: Re: FreeBSD I LOVE YOU X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 Jan 2005 14:51:07 -0000 Ian Moore wrote: > Tape de-gaussers usually aren't much good - they were mostly made for erasing > open reel tape that used ferric oxide particles. > Backup tapes normally use metal particle tapes that need a much stronger > magnetic field to effectively erase them. More powerful degaussers are available, like the one found at http://www.datalinksales.com/degaussers/hd1.htm Not cheap (about $5k if memory serves), but seems to do the job on both HDs and modern tapes (what the company calls "coercive media"). We have not found it necessary to remove the HD platters from their enclosures, although I imagine that might yield more thorough results. We just make two passes for better peace of mind. I also imagine that data on degaussed platters might still be available to the kinds of inspection techniques used on platters overwritten with random data, but our acceptable cost/reward balance tops off somewhere above preventing casual inspection and below stopping the NSA. One way that degaussing is more effective than random data writing is that the disk's servo tracks are also destroyed, meaning you'd probably need to return the device to the OEM for factory reconditioning before anyone could usefully attach it to another computer. I hope it's true, as that was our primary justification for the cost of the degausser. -- Greg Barniskis, Computer Systems Integrator South Central Library System (SCLS) Library Interchange Network (LINK) , (608) 266-6348