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Date:      Wed, 8 Aug 2012 18:55:14 +0300
From:      Nikolay Denev <ndenev@gmail.com>
To:        Brian Gold <bgold@simons-rock.edu>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: undoing zfs deduplication
Message-ID:  <63850C98-E472-40B9-8E7F-93FD6AC6B95E@gmail.com>
In-Reply-To: <0c8801cd757a$601018e0$20304aa0$@simons-rock.edu>
References:  <0c8801cd757a$601018e0$20304aa0$@simons-rock.edu>

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On Aug 8, 2012, at 6:27 PM, Brian Gold <bgold@simons-rock.edu> wrote:

> I've got a system running 9.0-release w/ a zfs v28 pool. Within that =
pool I have 3 datasets, two of which have deduplication
> enabled. I've recently been having a lot of performance issues with =
deduplication and have determined that I need far more ram that
> I currently have in order to support dedupe. I don't have the budget =
for the ram necessary so I would like to move away from
> deduplication. I'm aware  that you can't simply turn dedupe off, you =
need to completely nuke the filesystem.=20
>=20
> What I'm wondering is, would it be possible for me to create new =
datasets within the same pool (I have a ton of available space) and
> use a combination of "zfs send" & "zfs receive" to migrate my deduped =
datasets and all of their snapshots (daily, weekly, & monthly)
> over to the new dataset?=20
>=20
> Brian Gold
> System Administrator
> Bard College at Simon's Rock
>=20
>=20
>=20
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I believe simply disabling dedup should be enough.
Some blocks still will be just a "reference" to the original block =
because of the previously enabled deduplication, but this won't use =
additional memory.
New files will be written without being deduped.
If you want to de-dedup the files you can probably just "rsync $source =
$source.tmp && mv $source.tmp $source" in a loop to rewrite them.=



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