From owner-freebsd-hackers@FreeBSD.ORG Sat Jul 5 10:58:11 2014 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 5A8BB5DE for ; Sat, 5 Jul 2014 10:58:11 +0000 (UTC) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "funkthat.com", Issuer "funkthat.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 1B3402D3D for ; Sat, 5 Jul 2014 10:58:10 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id s65Aw9oQ026901 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 5 Jul 2014 03:58:10 -0700 (PDT) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id s65Aw9TK026900; Sat, 5 Jul 2014 03:58:09 -0700 (PDT) (envelope-from jmg) Date: Sat, 5 Jul 2014 03:58:09 -0700 From: John-Mark Gurney To: Jesse Gooch Subject: Re: geli+trim support Message-ID: <20140705105809.GH45513@funkthat.com> Mail-Followup-To: Jesse Gooch , freebsd-hackers@freebsd.org References: <7E2718485A3E405D89E5EAB331E9ED70@multiplay.co.uk> <53B6427D.1010403@gooch.io> <60445.1404461976@critter.freebsd.dk> <53B750C1.8070706@gooch.io> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53B750C1.8070706@gooch.io> User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Sat, 05 Jul 2014 03:58:10 -0700 (PDT) Cc: freebsd-hackers@freebsd.org X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 05 Jul 2014 10:58:11 -0000 Jesse Gooch wrote this message on Fri, Jul 04, 2014 at 18:11 -0700: > Hi, > > On 04/07/14 01:19 AM, Poul-Henning Kamp wrote: > > In message <53B6427D.1010403@gooch.io>, Jesse Gooch writes: > > > >> IIRC, TRIM is bad for encryption anyway. You want everything to be > >> random noise, even the empty sectors. TRIM defeats this. > > > > The problem is that there is nothing you can do. > > > > If you overwrite, your old sector is still unchanged somewhere in flash. > > > > If you TRIM, your old sector is still unchanged somewhere in flash, but > > if you're lucky for slightly less time. > > Perhaps I misunderstand TRIM, isn't the point of TRIM that it zeroes out > the sector ahead of time so it doesn't have to re-do it again when it > stores more data in that sector later? It is up the the implementation to choose what to do, depending upon spec.. For SATA, there are three options... One is non-deterministic read (meaning each read could return different data), one is deterministic read where each read returns the same value, but it is random data, and the third is data set to zero... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."