Date: Mon, 20 Jun 2011 21:55:13 -0700 From: Freddie Cash <fjwcash@gmail.com> To: "James L. Lauser" <james@jlauser.net> Cc: freebsd-fs@freebsd.org Subject: Re: ZFSv28 Dedup question Message-ID: <BANLkTinCXPfzqNPS5EGEw1b46mM9FaVD5g@mail.gmail.com> In-Reply-To: <BANLkTikZZg3W4zRED-Nj88y6kco_1qBehz2XJ2wq=Wj4Zj3Jsw@mail.gmail.com> References: <BANLkTikZZg3W4zRED-Nj88y6kco_1qBehz2XJ2wq=Wj4Zj3Jsw@mail.gmail.com>
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On Mon, Jun 20, 2011 at 7:46 PM, James L. Lauser <james@jlauser.net> 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
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