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Re: [Xen-users] Re: Will this work? (Zeroing free space)

  • To: Xen User-List <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
  • Date: Fri, 21 Aug 2009 17:10:47 +0700
  • Delivery-date: Fri, 21 Aug 2009 03:13:02 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>

On Fri, Aug 21, 2009 at 4:41 PM, Aleix Dorca<adorca@xxxxxx> wrote:
> I've also tried sdelete on a small VM and the backup has dropped from 5.6Gb
> to 3.4Gb on a 30Gb partition disk. Quite impressive.
> I've just also found "zerofree". A linux utility I didn't know about that
> zeros free space on ext2/3 filesystems. The device has to be unmounted
> though.

For Windows domU backup involving LVM snapshot, you might want to look
at ntfsclone. It has the benefit of saving only used ntfsblock without
having to run I/O-intensive zeroing application like sdelete first.
The downside, backup is done per domU partition, meaning you also need
a separate backup of domU's partition table and MBR (which rarely
change, so one-time backup should be enough).

I'm using it mainly to clone Windows domU, and it's working great for
Windows XP and 2003. To be specific, the cloning process includes:
- create partition table manually
- restoring a known good MBR
- restore data using ntfsclone
- ntfsresize if necessary

Using it for Windows 2008 is somewhat harder though, I've had some
non-working result. Probably related to ntfsclone version, more
testing needed.


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