wipe utility

[dsr at tao.merseine.nu]

On Thu, Sep 09, 2004 at 10:04:38PM -0400, James R. Van Zandt wrote:
> 
> >christoph at linuxsoup.com wrote:
> >
> >> I am just catching up on some email, but this thread caught my
> >> interest. I have [not] looked into the ext3 code or read any of the papers,
> >> but I was always under the impression that the filesystem journal only
> >> stored a bitmask (table) of modified blocks.  There shouldn't be any
> >> data in there.
> 
> [I'm even further behind in reading my email...]
> 
> ISTR that journaling filesystem can in general journal the data, but
> that really hurts performance, so most of them journal only the
> metadata.


mount options for ext3:

      data=journal / data=ordered / data=writeback

              Specifies  the  journalling  mode  for  file data.
              Metadata is always journaled.

              journal

                     All data is committed into the journal prior to
                     being written into the main file system.

              ordered

                     This is  the  default  mode.   All  data is forced
                     directly out to the main file system prior to its
                     metadata being committed to the journal.

              writeback

                     Data ordering is not preserved - data may be written
                     into the main file system after its metadata
                     has been committed to the journal.  This is
                     rumoured to be the highest-through)B­ put  option.
                     It  guarantees  internal file system integrity,
                     however it can  allow old data  to  appear  in
                     files after a crash and journal recovery.