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compressed disk image

Posted: 11 Feb 2010 15:55
by minipc
would it be possible to include the ability to create/handle compressed disk images in some future version of hxd? perhaps as "Save compressed disk image" and "Load compressed disk image" items in the "Extras" menu. i appreciate that this might not be a simple thing to do.

Re: compressed disk image

Posted: 26 Feb 2010 00:21
by Maël
I'll consider this, no promises though. Is there some kind of standard compressed image format?

Re: compressed disk image

Posted: 16 Jun 2010 15:53
by pTd
I've seen ZLib used in one disk imager. It's apparently good for stream-type compression.

Re: compressed disk image

Posted: 16 Jun 2010 20:45
by Maël
After some research it seems that VHD is a good disk image candidate, since it's openly documented and supported by various software packages including virtual machines. It also supports dynamic disks, that only store blocks that are non-null.

For compressing with support for random access, so as to make it possible to just read portions of the compressed disk image without decompressing it entirely (very slow for GB-sized files), bzip2 seems the most suited option (considering common compression formats): http://perldition.org/articles/Random%2 ... treams.sbc
LZMA may be faster in certain scenarios, but I am not sure about random access.

Wrt. to implementation time, I have no idea, currently, but it wont be part of the next release. (for alternatives in the mean time see also my other reply here: http://forum.mh-nexus.de/viewtopic.php?p=1132#p1132)

Re: compressed disk image

Posted: 18 Jun 2010 19:12
by pTd
Another old application called Selfimage uses bzip2 as an option. My example 160GB drive mentioned in the other thread compresses directly to about 12MB, further zipping to about 4MB. Undoubtedly it's a good option for large blank spaces. I don't think it's supported any longer, but it is open source.