[Gllug] Loopback mountable image file compression.

[James Laver]

On 22 Aug 2009, at 09:02, general_email at technicalbloke.com wrote:

> Hi there,
>
> 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. Can anyone offer  
> some
> advice as to which might be best for speed / compression / capacity /
> reliability etc.

Knoppix uses cloop, which takes their ~1.8GB image down to ~700mb ( so  
I guess about 2.5x ). It's read-only and it's fully transparent (as a  
kernel module).

I gather SquashFS is faster but less efficient at compression. I've  
noticed it's quite popular with non-knoppix liveCDs. There's also  
SquashFS-lzma you should look out for but I've not tested it, I've no  
idea about it's attributes or even it's stability.

--James
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