[Gllug] Loopback mountable image file compression.

[general_email at technicalbloke.com]

Richard Jones wrote:
> On Sat, Aug 22, 2009 at 09:02:54AM +0100, general_email at technicalbloke.com wrote:
>   
>> I have a need to make and archive dd images of windows machines but
>> naturally these are going to use a whole heap of space so I'd like to
>> compress them. Wanting also to eat my cake it would be nice to be able
>> to mount them as loopback devices without uncompressing the entire
>> volume first so straight ahead gzip and other stream compression progs
>> are out. I'm therefore wondering what block compression I could use:
>> cloop, squashfs or something else I've not heard of. It would need to
>> handle very large files, possibly multi terrabyte.
>>     
>
> Have you looked at qcow2?  The compression offered by qcow2 is block
> based, so it should perform much better than stream-based compression.
> (cloop is also block-based, but qcow has other features).
>
>   qemu-img convert -c -f raw input.img -O qcow2 output.qcow2
>   

Thanks for the suggestion Rich, I will look into it further soon as it
looks like it may be my only option now... cloop can't handle
filesystems bigger than a few gigs on my box (and is dog slow) and
SquashFS doesn't seem capable of taking input from stdin and so is of
little use to me.

Also, I found a prog that could make ntfs images recording only the
block that are in use (ntfsclone --save-image) but the image format is
not loop mountable :( Oh well, you can't have everything.


Cheers,

Roger.
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