[CentOS-virt] compress raw image

Charles Polisher

cpolish at surewest.net
Tue Aug 9 23:19:35 UTC 2011

Rainer Traut wrote:
> 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.
> Regards,
> Rainer

Don't forget rsync's parms --bwlimit=0 --compress-level=1


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