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Date:      Fri, 14 Jan 2022 18:10:21 +0100
From:      Ralf Mardorf <ralf-mardorf@riseup.net>
To:        questions@freebsd.org
Subject:   Re: zero filling a storage device (was: dd and mbr)
Message-ID:  <20220114181021.6c92db75@archlinux>
In-Reply-To: <20220114180039.4a1cf88e@archlinux>
References:  <77680665-7ddb-23c5-e866-05d112339b60@holgerdanske.com> <20220114023002.GP61872@eureka.lemis.com> <YeDryNdYe1S20wd2@neutralgood.org> <20220114045558.GQ61872@eureka.lemis.com> <20220114180039.4a1cf88e@archlinux>

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On Fri, 14 Jan 2022 18:00:39 +0100, Ralf Mardorf wrote:
>Hi,
>
>zero filling is fishy for several reasons. It's never secure!
>However, I won't comment zero filling. I'm not an expert and to lazy to
>search for links.
>
>Related to the addressable blocks and real physical locations I've got
>a link at hand.
>
>On Fri, 14 Jan 2022 15:55:58 +1100, Greg 'groggy' Lehey wrote:
>>proof of the contrary  
>
>Due to
>https://en.wikipedia.org/wiki/Wear_leveling
>the only way that could be (but not necessarily is) secure, is a secure
>erase command provided by the firmware.
>
>Regards,
>Ralf

PS: IIRC SSDs provide more disk space under the hood, than accessible by
a user. So you can't outwit wear leveling by overwriting the complete
disk. Probably it's still better to overwrite the complete accessible
disk space, than not to do so.



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