[CentOS-virt] compress raw image

Rainer Traut

tr.ml at gmx.de
Tue Aug 9 08:16:27 UTC 2011

Am 08.08.2011 18:51, schrieb Momo:
> Hi
>     No, he's talking filling with zeros unused blocks. That's a prerequisite
>     to optimize for a sparse image _on the other side_ and/or compression
>     during the transfer.
>     I know of an ext2/3/4 utility that does precisely that. I have no idea
>     if such an utility exists for NTFS.
> It exists for NTFS, have a look at "sdelete.exe" with -c option.

Sorry for getting back so late.

Yes, guys, exactly what I meant was filling unused space with zeros.
The linux tools to compress and transfer cannot read the ntfs data 
structure and compress every garbage. But if unused blocks are filled 
with zeros one can achieve much better compression.

I looked into sdelete.exe, this really is helpful but obviously works in 
running instance.

My idea is to mount the raw image with ntfs3g and create a big file with 
zeros. This should be sufficient, like Marco said.


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