CompactVD - reduce size of dynamic disk images

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CompactVD - reduce size of dynamic disk images

Postby Rui Baptista » 2. Nov 2016, 21:31

https://github.com/eternalbits/compactVD

CompactVD is a utility to optimize the size of dynamic disk images, based on the bitmap allocation tables of known file systems.

Supported file systems:
* Hierarchical File System (HFS), used in masOS computers
* Extended File System (EXT), used in most linux desktops

Last release has a simple implementation of Logical Volume Manager to reach file systems inside linear Logical Volumes with one Physical Volume. Although not interesting from a LVM point of view, many Linux servers start with a configuration like that.
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Re: CompactVD - reduce size of dynamic disk images

Postby socratis » 2. Nov 2016, 23:51

So, from reading the description at the GitHub, I get the idea that it sorts of combines the "zerofree"/"sdelete" with the "--compact" built-in option of VBoxManage, for EXT/HFS filesystems. Would that be my correct understanding?
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Re: CompactVD - reduce size of dynamic disk images

Postby Rui Baptista » 3. Nov 2016, 03:02

Yes, the result is analogous. Of course, zeros aren't actually written and I don't know what compact does internally... but that's it.
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Re: CompactVD - reduce size of dynamic disk images

Postby socratis » 3. Nov 2016, 04:45

OK, I'll give it a shot.

On a backup. It's a first release after all... ;)
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Re: CompactVD - reduce size of dynamic disk images

Postby mpack » 3. Nov 2016, 11:38

Interesting. Of course CloneVDI has had this exact compaction feature for 7 years - is there any source code in common? (translated from C to Java) ?

Though this does fill some interesting gaps: CloneVDI does support compaction of EXTx, but not HFS. And CloneVDI doesn't support LVM. In place editing is disallowed in CloneVDI as a matter of policy as it has obvious data safety implications.
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Re: CompactVD - reduce size of dynamic disk images

Postby Rui Baptista » 3. Nov 2016, 17:56

Hi, mpack, thank you for your interest.

This thing has evolved from a personal need for a HFS solution (as most of the open source), and therefore has no common parts with CloneVDI.

About editing in place, it is a convenient solution for less experienced users. For the conscientious ones there is a copy option :)
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Re: CompactVD - reduce size of dynamic disk images

Postby mpack » 3. Nov 2016, 18:09

Rui Baptista wrote:About editing in place, it is a convenient solution for less experienced users. For the conscientious ones there is a copy option :)

Well, of course it's precisely the less experienced users who will not understand the wisdom of making a backup copy.

VBoxManage also does e.g. resizing in place. I had these same comments back then, but I was a lone voice. And, just as I suspected, there have been several disasters where inexperienced uses have destroyed their virtual drives because of a host glitch that happened while resizing, or who simply got the resize command arguments wrong. Of course compaction shouldn't have the room for user error that resizing does.
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