From owner-freebsd-questions@FreeBSD.ORG Mon Nov 8 15:37:51 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id D0BC7106564A for ; Mon, 8 Nov 2010 15:37:51 +0000 (UTC) (envelope-from freebsd@qeng-ho.org) Received: from blue.qeng-ho.org (blue.qeng-ho.org [217.155.128.241]) by mx1.freebsd.org (Postfix) with ESMTP id 5D0688FC23 for ; Mon, 8 Nov 2010 15:37:51 +0000 (UTC) Received: from fileserver.home.qeng-ho.org (localhost [127.0.0.1]) by fileserver.home.qeng-ho.org (8.14.4/8.14.4) with ESMTP id oA8Fbnwb021071 for ; Mon, 8 Nov 2010 15:37:49 GMT (envelope-from freebsd@qeng-ho.org) Message-ID: <4CD8194D.7080208@qeng-ho.org> Date: Mon, 08 Nov 2010 15:37:49 +0000 From: Arthur Chance User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US; rv:1.9.1.15) Gecko/20101030 Thunderbird/3.0.10 MIME-Version: 1.0 To: FreeBSD-Questions References: <20101106203016.GB13095@guilt.hydra> <20101106213836.GA77198@slackbox.erewhon.net> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: ZFS License and Future X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Nov 2010 15:37:51 -0000 On 11/08/10 13:52, krad wrote: > On 6 November 2010 21:38, Roland Smith wrote: > >> On Sat, Nov 06, 2010 at 02:30:16PM -0600, Chad Perrin wrote: >>>> Having said all that it really depends on whether you need the extra >>>> features of zfs. Personally I cant see how anyone with any important >> data >>>> can do without checksuming. >>> >>> I guess that depends on what you're doing with the data and what kind of >>> external tools you have in place to protect/duplicate it in case of a >>> problem. >> >> The GEOM_ELI class provides optional authentication/checksumming. See >> geli(8), >> especially the -a option. >> >> Roland >> -- >> R.F.Smith http://www.xs4all.nl/~rsmith/ >> [plain text _non-HTML_ PGP/GnuPG encrypted/signed email much appreciated] >> pgp: 1A2B 477F 9970 BA3C 2914 B7CE 1277 EFB0 C321 A725 (KeyID: C321A725) >> > > im not sure on whether that you be a viable replacement, as it has to be a > fairly good checksum to avoid clashes, whilst also being quick so it doesnt > adversly affect disk performance. Also what does it do if it detects the > checksum doesnt match etc? Good point. Geli uses a crypto standard hash (HMAC/SHA256 is recommended) as it's all about authentication in the face of potentially malicious attack, and that's fairly expensive. ZFS by default uses the fletcher2 (= fletcher32) hash, which is simple and fast, as it's used to make sure that hardware hasn't accidentally mangled your data. -- "Although the wombat is real and the dragon is not, few know what a wombat looks like, but everyone knows what a dragon looks like." -- Avram Davidson, _Adventures in Unhistory_