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Date: Mon, 13 Aug 2012 22:15:50 +0200
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From: Olivier Smedts <olivier@gid0.org>
To: Steven Schlansker <stevenschlansker@gmail.com>
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Cc: freebsd-fs@freebsd.org, Petri Helenius <petri@helenius.fi>
Subject: Re: zero deleted blocks
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2012/8/13 Steven Schlansker <stevenschlansker@gmail.com>:
>
> On Aug 13, 2012, at 2:27 AM, Olivier Smedts <olivier@gid0.org> wrote:
>> Did you try a classic "dd if=/dev/zero of=a-file-on-the-pool" ? This
>> won't give good results if you do this on a filesystem with
>> compression enabled.
>
> ZFS uses copy on write (http://en.wikipedia.org/wiki/ZFS#Copy-on-write_transactional_model) so overwriting with zeroes will actually allocate new space to hold all the zeroed data and leave the old data mostly untouched.

Only until all the free space is consumed !

-- 
Olivier Smedts                                                 _
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