compressed disk image

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minipc
Posts: 1
Joined: 11 Feb 2010 15:42

compressed disk image

Post by minipc » 11 Feb 2010 15:55

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.

Maël
Site Admin
Posts: 1160
Joined: 12 Mar 2005 14:15

Re: compressed disk image

Post by Maël » 26 Feb 2010 00:21

I'll consider this, no promises though. Is there some kind of standard compressed image format?

pTd
Posts: 18
Joined: 22 Sep 2009 18:16

Re: compressed disk image

Post by pTd » 16 Jun 2010 15:53

I've seen ZLib used in one disk imager. It's apparently good for stream-type compression.
Last edited by pTd on 18 Jun 2010 17:03, edited 1 time in total.

Maël
Site Admin
Posts: 1160
Joined: 12 Mar 2005 14:15

Re: compressed disk image

Post by Maël » 16 Jun 2010 20:45

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)

pTd
Posts: 18
Joined: 22 Sep 2009 18:16

Re: compressed disk image

Post by pTd » 18 Jun 2010 19:12

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.

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