Date: Mon, 08 Nov 2010 15:37:49 +0000 From: Arthur Chance <freebsd@qeng-ho.org> To: FreeBSD-Questions <freebsd-questions@freebsd.org> Subject: Re: ZFS License and Future Message-ID: <4CD8194D.7080208@qeng-ho.org> In-Reply-To: <AANLkTi=7MhvRTLP1NzGaHQFsV=FU8QDn5K73EmLPZH2k@mail.gmail.com> References: <AANLkTi=dKatHYLFhC35VTT4fCAKgYLKEri2yVCPtSv7g@mail.gmail.com> <AANLkTinxLcrRoB6b2AcTrxHLqRCkyoWUhU=EmuvzEZQ8@mail.gmail.com> <20101106203016.GB13095@guilt.hydra> <20101106213836.GA77198@slackbox.erewhon.net> <AANLkTi=7MhvRTLP1NzGaHQFsV=FU8QDn5K73EmLPZH2k@mail.gmail.com>
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On 11/08/10 13:52, krad wrote: > On 6 November 2010 21:38, Roland Smith<rsmith@xs4all.nl> 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/<http://www.xs4all.nl/%7Ersmith/>; >> [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_
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