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I'm defragmenting my hard drive (XP SP3) with PerfectDisk 7.0, and it finds 816,659 excess fragments when I ask for an analysis.

[update] Specifically, it shows that the 1TB disk is 14% fragmented with 19693 fragments and 816,659 excess fragments. About 20% of the disk is still free space.

What does excess fragments refer to? What is the difference between fragments and excess fragments?

I have had problems in the past where I defragmented a fragmented disk and many files were corrupted. It seemed as though "excess fragments" referred to orphan pieces, where the program couldn't find out where to put them.

If that was true, then defragmenting a disk resulted in many incomplete files, and in fact I defragmented a disk full of MP3's and got a lot of corrupted files as a result.

Instead, I started to simply format a separate disk and copy everything from one to the other. That way there were no orphan bits, and no file corruption.

Does anybody know what "excess fragments" really are?

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Please cite that PerfectDisk is the defragmenter that shipped as part of Windows XP. I do not believe this is the case. –  ChrisInEdmonton Nov 6 '09 at 16:32
    
Based on support.microsoft.com/kb/314848, it looks as though it DiskKeeper that is the same as the XP deframentation utility. I seem to remember reading that PerfectDisk was an evolution of the same utility, but I can't find any sources right now. I'll keep looking. –  Andrew Swift Nov 6 '09 at 18:07
    
No biggie, of course, I just am dubious that PerfectDisk is included in XP. –  ChrisInEdmonton Nov 6 '09 at 18:34
    
wegotserved.com/2009/02/03/… seems to indicate that diskeeper is separate to perfectdisk, but one could indeed have been a branch of the other. Either way, no big deal. –  ChrisInEdmonton Nov 6 '09 at 18:36
    
Why would it be hard to believe? DiskKeeper, with minor changes, was included with XP... Those changes just disabled the behind the scenes operation... And they upsold the non-modified version for a heck of a price tag... –  Benjamin Schollnick Nov 6 '09 at 18:58

4 Answers 4

up vote 1 down vote accepted

Excess fragments, otherwise called extra file fragments, are explained in CrackUp Alerts You to Disk Fragmentation:

Each contiguous portion of a file's cluster chain is called a fragment. An unfragmented file consists of a single fragment; a fragmented file consists of two or more fragments. By definition, the first portion of a file's cluster chain (its first fragment) is not fragmented. Therefore a disk can never be 100 percent fragmented. Fragments beyond the first are called extra fragments. The more extra fragments, the more fragmented the file. A file is maximally fragmented when the number of fragments equals the number of clusters. In other words, each of that file's fragments consists of a single cluster.

Therefore, the excess fragments total means the number of fragments that ideally should be eliminated by a 100% successful defrag. But in real life, several successive defrags are necessary to bring their number anywhere near to zero, and at least 20% of disk free space.

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On C: I have 157,602 files. However, in PerfectDisk, there are only 19713 fragments (and 817355 excess fragments). There are many more files than fragments (according to PCMag, each file should represent at least one fragment). Still, this explanation of extra fragments makes sense, and the PCMag reference is useful. Thanks! –  Andrew Swift Nov 9 '09 at 12:02

Excess fragments is not orphaned parts of files.
It is a set of fragments that remained after the de-fragmentation completed (or at the end of a fragmentation analysis maybe).

If de-fragmentation left you with corrupted files,
you may have a bad disk where the data was moved from good sectors to bad ones,
causing you to see corruption in files which were earlier not-corrupted.

De-frag technology today does not corrupt a drive even if you lose power halfway through a de-frag operation.

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Do you have any references or links? –  Andrew Swift Nov 6 '09 at 10:03
3  
To say modern defragmenters can not cause corruption in a powerloss situation is a little inaccurate. Good defragmenting code should not cause any corruption if used on a filesystem that journals at least filesystem metadata such as ext3/4 in default settings and NTFS. It is the journal that saves you from the corruption so unjournalled fileystems (ext2, ext3/4 with the journal off, FAT16/32/related) are still potentially prone to the issue. –  David Spillett Nov 6 '09 at 11:02
    
I agree with David's points. And Andrew, I cannot locate references at the moment. Will add in if I can get any. –  nik Nov 6 '09 at 11:22

How much disk space is free on the drive, and how much of it is contingious? It maybe that the larger files can't be defragmented, since there is not enough contingious free space available to store that file in.

Thus causing excess fragments....

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I added some information to the question -- there are about 200GB free, much bigger than the biggest fragmented file. And, in addition to the excess fragments there are "regular" fragments. –  Andrew Swift Nov 6 '09 at 16:28

Just a guess, but I think the excess fragments might be page file fragments that cannot be defragmented from within Windows. You need to do a boot-time defrag to defrag the page file. Not sure if Perfectdisk offers this feature, but Diskeeper Pro 2009 that I use has this option. Diskeeper automatically defrags all files from within XP, except notably the page file, which requires the aforementioned boot defrag.

If your files are getting corrupted after a defrag, then there is some filesytem problem, since defrag never changes the contents of a file, it merely makes the file contiguous. You should run chkdsk with the /r switch to scan for and fix these errors. http://support.microsoft.com/kb/315265

PS: Perfectdisk is different from Diskeeper. The latter and Microsoft jointly developed the defrag API used in all windows versions since XP. In fact the XP defragger was a heavily stripped down version of some Diskeeper product from the early 2000s

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