SHRED for EXT3?

[Les Mikesell]

On Wed, 2005-07-27 at 23:54, Michael Hennebry wrote:

> man shred
> ...
> CAUTION:  Note  that shred relies on a very important assumption: that
> the filesystem overwrites data in place.  This is the traditional  way
> to  do  things, but many modern filesystem designs do not satisfy this
> assumption.  The following are examples of filesystems on which  shred
> is not effective:
> 
> * log-structured or journaled filesystems, such as those supplied with
> 
>        AIX and Solaris (and JFS, ReiserFS, XFS, Ext3, etc.)

Do any of these actually journal the data portion of the file in
a default installation?  I thought they typically only do the
metadata to keep the free/used space consistent if the update
is interrupted.  There would be a severe performance penalty if
they actually write everything twice.

One instance where the overwrite would not work would be
an LVM where one or more snapshots are currently active
keeping the old copy from being changed.

-- 
  Les Mikesell
    lesmikesell at gmail.com