Registry Defragmenter

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Registry Defragmenter

Hello folks,

This is out of curiosity, but I have seen several (and some of them very popular) software called registry defragmenter. While I can see the benefit they offer, but I am very curious on how exactly do you do registry defragmenting? Note that I'm not asking for software name, just a basic description of how it's done programmatically. I understand there is disk defragmenting API from microsoft. Is this that they are using? Or is there "registry defragmenting" api?

I suspect they're just defragmenting the files used to store registry information. Since the registry files are open during all normal Windows operation, a "normal" file defragmenting tool won't even touch them.

Jerry Coffin 2010-10-06 20:08:22

Initially I suspect that too. But like wallyk mentioned, many claim they do reordering registry nodes (as to children keys placed right next to the parent).

DonnVall 2010-10-06 20:40:38

Btw, I have seen JkDefrag (now MyDefrag) defragmenting paging files. So ordinary defragmenting tool should be able to defrag registry files.

DonnVall 2010-10-06 20:44:05

While disk defragmenting would be helpful, the more important speed benefit which could be obtained would be arranging the registry nodes so that a typical depth-first search would put the sequentially-accessed nodes in the same registry page.

I'm not aware of any API for that. The algorithm is a straightforward reordering and rewriting operation, complicated by dealing with Windows' concurrent access.

wallyk 2010-10-06 20:08:57

Do you suggest they actually understand the registry file format? Gotta fire up my hex editor... :)

DonnVall 2010-10-06 20:46:52

There are tools out there that read the raw registry hive files. Check out some of the open source password crackers or forensic tools.

Anders 2010-10-06 20:52:25

The registry file format is nothing too complicated. View the raw hex format is unenlightening, but there are some documents floating around that are more or less correct. See http://www.sentinelchicken.com/data/TheWindowsNTRegistryFileFormat.pdf

wallyk 2010-10-06 22:03:23

@Anders, done! Found some "interesting" projects in sourceforge.net.

DonnVall 2010-10-07 08:10:15

So in the end it's just moving the file content? Personally, after I learn how it is done, I don't like it. Mainly because they don't use (since there is none - I believe) official information from Microsoft. A tiny misunderstanding could easily screw up users' machines. On the other side I also respect the team behind those software for they manage not to wreaking havoc so far. :)

DonnVall 2010-10-07 08:17:13

Well, testing such a utility is fairly easy: Windows tends to crash and not ever boot again if the registry is munged.

wallyk 2010-10-07 17:50:51

ansaurus

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Registry Defragmenter

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