From owner-svn-doc-projects@FreeBSD.ORG Thu Oct 3 15:44:44 2013 Return-Path: Delivered-To: svn-doc-projects@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 2EA39899; Thu, 3 Oct 2013 15:44:44 +0000 (UTC) (envelope-from kaduk@mit.edu) Received: from dmz-mailsec-scanner-2.mit.edu (dmz-mailsec-scanner-2.mit.edu [18.9.25.13]) by mx1.freebsd.org (Postfix) with ESMTP id 9E2192CDB; Thu, 3 Oct 2013 15:44:43 +0000 (UTC) X-AuditID: 1209190d-b7f528e0000009b4-7e-524d90eabb1a Received: from mailhub-auth-2.mit.edu ( [18.7.62.36]) by dmz-mailsec-scanner-2.mit.edu (Symantec Messaging Gateway) with SMTP id B0.A8.02484.AE09D425; Thu, 3 Oct 2013 11:44:42 -0400 (EDT) Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by mailhub-auth-2.mit.edu (8.13.8/8.9.2) with ESMTP id r93FifwD018827; Thu, 3 Oct 2013 11:44:41 -0400 Received: from multics.mit.edu (system-low-sipb.mit.edu [18.187.2.37]) (authenticated bits=56) (User authenticated as kaduk@ATHENA.MIT.EDU) by outgoing.mit.edu (8.13.8/8.12.4) with ESMTP id r93FidAv023123 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Thu, 3 Oct 2013 11:44:40 -0400 Received: (from kaduk@localhost) by multics.mit.edu (8.12.9.20060308) id r93FidfY029688; Thu, 3 Oct 2013 11:44:39 -0400 (EDT) Date: Thu, 3 Oct 2013 11:44:38 -0400 (EDT) From: Benjamin Kaduk To: Benedict Reuschling Subject: Re: svn commit: r42810 - projects/zfsupdate-201307/en_US.ISO8859-1/books/handbook/zfs In-Reply-To: <201310022100.r92L07qP038968@svn.freebsd.org> Message-ID: References: <201310022100.r92L07qP038968@svn.freebsd.org> User-Agent: Alpine 1.10 (GSO 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrNIsWRmVeSWpSXmKPExsUixG6novtqgm+Qwd9PYhbnj6hb/Ph4iMli 4ZnVzA7MHjM+zWcJYIzisklJzcksSy3St0vgynjesYqtYJNgxaz9zSwNjNP4uhg5OSQETCR2 7P3NDGGLSVy4t56ti5GLQ0hgH6PEmU097CAJIYENjBLLdnhCJA4ySUx8tYkVIlEv0f92CyOI zSKgJTH70ikmEJtNQEVi5puNbCC2iICmxOy21WBxZgEbiQkPFoANFRZIkJj9D2Izp4CVxLqL /WBxXgFHiTcr7kPNt5R4svgmmC0qoCOxev8UFogaQYmTM5+wQMy0lPi39hfrBEbBWUhSs5Ck FjAyrWKUTcmt0s1NzMwpTk3WLU5OzMtLLdI10svNLNFLTSndxAgKU05J3h2M7w4qHWIU4GBU 4uFlyPcNEmJNLCuuzD3EKMnBpCTKm98LFOJLyk+pzEgszogvKs1JLT7EKMHBrCTCy1YFlONN SaysSi3Kh0lJc7AoifPe5LAPEhJITyxJzU5NLUgtgsnKcHAoSfDyA+NRSLAoNT21Ii0zpwQh zcTBCTKcB2j4u36Q4cUFibnFmekQ+VOMilLivBogzQIgiYzSPLheWBp5xSgO9Iow7x+Qdh5g CoLrfgU0mAlocJQE2OCSRISUVANjStRkqWpjqfDzW90NTdW3SF66c6U0bVfW3Rdbp574sI01 ab7uw19L0o9WcNrGWa+sWXDYzHGL1U638gzVM20ZlgFbj1ntV/D9ueRD2aJ3649wm31uLn92 6P7bx0s/Rl5vfc3aaVJxa9ZiYaW1u55nC06MmXNNUfbC/aorKo+nL/8tEBB9IV+YR4mlOCPR UIu5qDgRAK7kkx7+AgAA Cc: svn-doc-projects@freebsd.org, doc-committers@freebsd.org X-BeenThere: svn-doc-projects@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: SVN commit messages for doc projects trees List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 03 Oct 2013 15:44:44 -0000 On Wed, 2 Oct 2013, Benedict Reuschling wrote: > Author: bcr > Date: Wed Oct 2 21:00:07 2013 > New Revision: 42810 > URL: http://svnweb.freebsd.org/changeset/doc/42810 > > Log: > Add a section on deduplication. This needs some more work and warnings about > huge memory requirements for the DDT. But the basic instructions are there on > how to activate it, along with an example that shows the dedup ratio and > a simulation run with zdb. > > Modified: projects/zfsupdate-201307/en_US.ISO8859-1/books/handbook/zfs/chapter.xml > ============================================================================== > --- projects/zfsupdate-201307/en_US.ISO8859-1/books/handbook/zfs/chapter.xml Wed Oct 2 20:02:02 2013 (r42809) > +++ projects/zfsupdate-201307/en_US.ISO8859-1/books/handbook/zfs/chapter.xml Wed Oct 2 21:00:07 2013 (r42810) > + > + The DEDUP column shows the actual rate > + of deduplication for that pool. A value of > + 1.00x that no data has been deduplicated > + due to insufficient duplicate data. In the following example, > + the ports tree is copied three times into different > + directories on the deduplicated pool above to provide > + redundancy. I'm not sure that this is the best way to talk about an example use-case where deduplication would come into play. If the user actually wants redundancy (that is, to ensure that there is a reliable/correct copy of the ports tree around in the event of hardware issues), deduplication is not the right tool, 'zfs set -o copies=3' would be more appropriate. The whole point of the deduplication is that there is only one actual copy on disk. It would probably be a better example to talk about copying the ports tree three different times for testing different configurations or something like that. -Ben > + &prompt.root; zpool list > +for d in dir1 dir2 dir3; do > +for> mkdir $d && cp -R /usr/ports $d & > +for> done > + > + Now that redundant data has been created, ZFS detects that > + and makes sure that the data is not taking up additional > + space.