From owner-freebsd-fs@FreeBSD.ORG Tue Jun 21 04:55:14 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 582AE1065670 for ; Tue, 21 Jun 2011 04:55:14 +0000 (UTC) (envelope-from fjwcash@gmail.com) Received: from mail-gx0-f182.google.com (mail-gx0-f182.google.com [209.85.161.182]) by mx1.freebsd.org (Postfix) with ESMTP id 0E6AD8FC0C for ; Tue, 21 Jun 2011 04:55:13 +0000 (UTC) Received: by gxk28 with SMTP id 28so2412027gxk.13 for ; Mon, 20 Jun 2011 21:55:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=gCT1CIVQzf1cFBJXpeCF8qclBdYgc0OUTiZ96SeV5pc=; b=lZD46eCh1bb3O2S0Fg/XMCHVQDysf4cTdQ3ssVIaSyoZt/7IxeiFnPsmpD0wpNWzdW ME9UcWuQLDMtpjCanbU8bP85CzU57ff+TQPqBbcTLPyoo0hzB/2kCWJKEfnN2SPEbwbC 3nd+D+x+FA+y/DFzzsI7I5fcGLNWg6m9wfMUw= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=Go8Mi/vuiIkzfIv4M63CHV1rcC0qgK+BkzkYWz0zFMM1YERsM6/+0AcV8FiWY/nK31 qMrJM9u1ou8JHoYkLiIe1CtWyspQyiuejqvD4Y6fSW7CxgeoCGB728awU29QykBLIAu6 7HbbjKgCHw1077+kqg1mEtV9JGgrqZ6JcldAU= MIME-Version: 1.0 Received: by 10.91.66.15 with SMTP id t15mr6596776agk.141.1308632113185; Mon, 20 Jun 2011 21:55:13 -0700 (PDT) Received: by 10.90.65.18 with HTTP; Mon, 20 Jun 2011 21:55:13 -0700 (PDT) In-Reply-To: References: Date: Mon, 20 Jun 2011 21:55:13 -0700 Message-ID: From: Freddie Cash To: "James L. Lauser" Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-fs@freebsd.org Subject: Re: ZFSv28 Dedup question X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Jun 2011 04:55:14 -0000 On Mon, Jun 20, 2011 at 7:46 PM, James L. Lauser wrote: > I have a (hopefully) simple question about ZFSv28 deduplication that is not > very clearly answered in any of the documentation I've found. > > If I enable dedupe on a dataset, will newly written data dedupe against old > data that was written before dedupe was enabled? If not, is it worth > forcing the data to be rewritten so that it makes it into the appropriate > tables? > > No. Dedupe only applies to newly written data. The DDT (dedupe table) only contains entries for data written after the "dedup" property is set on a filesystem. The only way to dedupe existing data is to copy/delete it, or "zfs send|zfs recv" it, or otherwise re-write it. -- Freddie Cash fjwcash@gmail.com