From owner-freebsd-fs@FreeBSD.ORG Sun Aug 15 00:06:59 2004 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7F09816A4CE for ; Sun, 15 Aug 2004 00:06:59 +0000 (GMT) Received: from maui.ebi.ac.uk (maui.ebi.ac.uk [193.62.196.100]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4006843D3F for ; Sun, 15 Aug 2004 00:06:58 +0000 (GMT) (envelope-from kreil@ebi.ac.uk) Received: from puffin.ebi.ac.uk (puffin.ebi.ac.uk [193.62.196.89]) by maui.ebi.ac.uk (8.11.7+Sun/8.11.7) with ESMTP id i7F06tF23495; Sun, 15 Aug 2004 01:06:55 +0100 (BST) Received: from puffin.ebi.ac.uk (kreil@localhost) by puffin.ebi.ac.uk (8.11.6/8.11.6) with ESMTP id i7F06s717877; Sun, 15 Aug 2004 01:06:55 +0100 Message-Id: <200408150006.i7F06s717877@puffin.ebi.ac.uk> X-Mailer: exmh version 2.4 06/23/2000 with nmh-1.0.4 To: Brooks Davis In-Reply-To: Your message of "Fri, 13 Aug 2004 22:09:03 PDT." <20040814050903.GA20113@Odin.AC.HMC.Edu> X-Habeas-SWE-1: winter into spring X-Habeas-SWE-2: brightly anticipated X-Habeas-SWE-3: like Habeas SWE (tm) X-Habeas-SWE-4: Copyright 2002 Habeas (tm) X-Habeas-SWE-5: Sender Warranted Email (SWE) (tm). The sender of this X-Habeas-SWE-6: email in exchange for a license for this Habeas X-Habeas-SWE-7: warrant mark warrants that this is a Habeas Compliant X-Habeas-SWE-8: Message (HCM) and not spam. Please report use of this X-Habeas-SWE-9: mark in spam to . Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Sun, 15 Aug 2004 01:06:54 +0100 From: David Kreil X-EBI-Information: This email is scanned using www.mailscanner.info. X-EBI: Found to be clean X-EBI-SpamCheck: not spam, SpamAssassin (score=-8, required 5, HABEAS_SWE -8.00) cc: freebsd-fs@freebsd.org cc: David Kreil Subject: Re: "sanitizing" disks: wiping swap, non-allocated space, and file-tails X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 15 Aug 2004 00:06:59 -0000 Dear Brooks, Thank you very much for your fast and friendly response. > > > > > > > The easiest way to scrub a disk is: > > > > > > > > > > > > > > dd if=/dev/random of=/dev/ bs= > > > > > > > > > > > > > > > I noticed that it will refuse to let me do that on swap, even if it is > > > > of f. Of course, I can edit the disklabel to read "unused", run dd, > > > > and restore the swap disklabel to "swap" but is there another way? > > > > > > That's broken. Which OS are you using? > > > > Don't know whether I answered that before: 5.2.1-RELEASE-p9/GENERIC > > To which list, if not fs, should I send a bug-report in your opinion? > > It would help if you could test this under CURRENT. The -geom list is > probably a good place to report this as it's probably a geom issue > (though it's possiably it's actually a swap issue). Ok, I'll try and get CURRENT checked out and compiled and test it there, too. > > apparently on its way breaking down) and now get ~50MB/s write > > performance for dd if=/dev/zero, and ~13MB/s for /dev/random. So if > > I could generate good pseudo-random numbers fast enough, I should be > > able to wipe a 10GB partition 20x in an hour - that's good enough! > > The arc4random call will be good enough for most purposes, especially is > you reseed it before each run and discard the first 256 bytes. > > [...] > > > > I've got such an application, but I haven't had time > > > to clean it up and submit it for release. I'll probably do it some day, > > > but I can't recommend waiting for that. It's only about 800 lines of > > > code including the man page and a fancy composable operations system to > > > allow just about any DoD or non-DoD pattern or writes and verifies to be > > > written on the command line. > > > > I'd be grateful if you could make your utility available. All I need > > is random patterns (white noise). Would that be possible at all, > > please? > > My program can do that. I'll see what I need to do to get it released. That is great, thank you very much! > It may take a little while. I understand. Can you give me a rough idea at all of when you might find the time? With many thanks again and best regards, David. ------------------------------------------------------------------------ Dr David Philip Kreil ("`-''-/").___..--''"`-._ Research Fellow `6_ 6 ) `-. ( ).`-.__.`) University of Cambridge (_Y_.)' ._ ) `._ `. ``-..-' ++44 1223 764107, fax 333992 _..`--'_..-_/ /--'_.' ,' www.inference.phy.cam.ac.uk/dpk20 (il),-'' (li),' ((!.-'