Message-Id: <200411301914.iAUJEAJx001591@turing-police.cc.vt.edu>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: John Richard Moser <nigelenki@comcast.net>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Designing Another File System 
In-Reply-To: Your message of "Tue, 30 Nov 2004 17:46:10 GMT."
             <1101836768.25629.66.camel@localhost.localdomain> 
From: Valdis.Kletnieks@vt.edu
References: <41ABF7C5.5070609@comcast.net> <200411301828.iAUISgf8031548@turing-police.cc.vt.edu>
            <1101836768.25629.66.camel@localhost.localdomain>
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On Tue, 30 Nov 2004 17:46:10 GMT, Alan Cox said:
> On Maw, 2004-11-30 at 18:28, Valdis.Kletnieks@vt.edu wrote:
> > On Mon, 29 Nov 2004 23:32:05 EST, John Richard Moser said:
> > they punt on the issue of over-writing a sector that's been re-allocated by
> > the hardware (apparently the chances of critical secret data being left in
> > a reallocated block but still actually readable are "low enough" not to wor
ry).
> 
> I guess they never consider CF cards which internally are log structured
> and for whom such erase operations are very close to pointless.

The 3-overwrites is for "rigid disks" only, and for "sanitize" operations
required when the media is being released from continuous protection (basically,
when you're disposing of the drive).  Clearing (for when the drive is being
kept, but re-used) only requires 1 pass.  A CF card would be handled
under different rules - I'm pretty sure it would be treated as the appropriate
class of "memory" (but admit not knowing which technology it would be).

See "Clearing and sanitization matrix" from the bottom of:
http://www.dss.mil/isec/chapter8.htm


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