defragger : Java Glossary

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defragger  defragger
Introduction O & O Defragger
Tips Smart Defrag
Defragger Products Symantec Norton SpeedDisk
Systems Internals PageDefrag Difficult To Defrag Files
Built-In Windows Defragger Defragging the Pagefile
JkDefrag Feature Comparison Matrix
Auslogics Disk Defrag Keeping Files Defragged
DiskTrix Ultimate Defrag SSDs
Abelssoft JetDrive The Ideal Defragger
Condusiv Diskeeper Summary
Raxco Perfect Disk Links


A defragger is a utility that ensures files on disk are in one contiguous chunk. A defragger may also position files on disk so that frequently used files get prime real estate. The outermost tracks (beginning of the disk) have faster transfer rate because they are longer and hence pack more data per revolution. They are also faster because they are near the prime OS (Operating System) system areas where the heads tend to hover over. Ideally it would order files by last access date, perhaps weighted by frequency of use statistics. That way all your hot files are close together and files that end to be used together live side by side. It may also defrag and tidy directories and other system tables. It may consolidate free space fragments.

Windows has an official NTFS (New Technology File System) defrag interface. It is extremely conservative and slow. The idea is that defraggers can safely run while other programs are running simultaneously messing up the disk. Another advantage of the interface is that bugs in the defragger are very unlikely to corrupt the disk. Further, system crashes while a defragger is running are also very unlikely to corrupt the disk. It would be much faster if Microsoft would implement it properly. It should buffer up several requests to move small files and move a batch of them (or file fragments) in one single elevator seek. The interface could stay the same. It would just have some extra intelligence inside to do the moves slightly out of order, in batches.


Defragger Products

Windows Hard Disk Defraggers
Product Version Price in
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Strengths Weaknesses
Systems Internals PageDefrag 2.32 free defrags pagefile.sys file. For NT, W2K and XP. Does nothing else besides defrag pagefile.sys Can only run at boot time. You can almost as easily and more safely, defrag pagefile.sys by temporarily moving it to another partition in the Control Panel, reboot, defrag, then move it back, then reboot again. However, you need a spare FAT (File Allocation Table) or NTFS partition to do that.
Built-In Windows defragger free This is the defragger that comes bundled with Windows. It is a stripped down version of Norton Defrag that does not attempt to place most commonly used files in prime real estate — half the purposes of a defragger.
MyDefrag 4.3.1 free née JkDefrag. Open source, source available. Script driven. Can order by last access date. Bare bones. Purely command line driven. You need the -f 0 option or similar to make it work sensibly. It cannot defrag locked or system files.
Auslogics Disk Defrag Auslogics Disk Defrag $30.00 USD for pro version. Also free version.
Last revised/verified: 2018-02-06
Works on W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32 and W8-64. Quick. Comes in 32 and 64-bit versions. Has boot time defrag to defrag some of the system files which they call offline defrag. It has a special defrag algorithms for SSDs (Solid State Disks) to avoid wearing them out with too many writes. It has a special mode to use if you are creating system checkpoints. Allows simple defrag, free space consolidation, by prefetch layout and by disk zone (last modified timestamp). Has a wizard that configures various types of background defrags at various times just by answering a few non-technical questions. You can configure it not to run with a given list of important apps are running. It will automatically get rid of various types of junk files before defrag. It is straightforward and quick. Has accurate easy-to-understand progress bars. It has special logic for SSD (Solid State Disk) drives. Does not have a way of handling all the locked or system files.
Disktrix Ultimate Defrag
DiskTrix Ultimate Defrag $30.00 USD They give you a $10 coupon when you download the trial you must use in 5 days.
Last revised/verified: 2016-04-11
  • Supports XP, W2003, Vista, W2008, W7-32 and W7-64. I suspect it also works on W8-32, W8-64, W2012, W10-32 and W10-64, but their website does not state that.
  • It has come a long way since I first tested it in 2005.
  • If you let it do a boot-time defrag, it can defrag everything, even system files like the MFT (Master File Table) , pagefile.sys, $Logfile, hiberfile.sys, $USN ChangeJournal… Not only will it let you defrag these files, it will let you precisely place them.
  • I have not done a formal benchmark, but this feels like the fastest defragger.
  • It claims monitors file use between defrags to figure out which files you use most often. I suspect this is not literally true. I can see so sign of any service doing such monitoring. I think all they means in they turn on the OS last-access tracking. They are thus tracking when files were last used, but not how often. The most used files it moves to the prime real estate near the edge of the disk. If this were true, it would be an incredibly brilliant feature. I have not noticed any major improvement in performance after using it. It has a file usage database that it updates each time you run the defragger. Perhaps it snapshots the last-access dates of all the files, noticing changes to get an estimate of frequency of use.
  • It is quite clever deciding its moves. It avoids having to move the same file over and over because its ultimate location is occupied. It sometimes cleverly copies files starting at the end to accommodate a slide toward the center of the disk.
  • The defrag is remarkably quick in all of the modes. It lets you look at and start defrags on other partitions even when it is busy defragging. It is completely responsive even when it is defragging.
  • It offers you a choice of you five basic algorithms, basically trading off precision for speed. It has many sub options. You can sort by create date, last access date, last modified date. Its normal mode is to place files in three zones (outer high performance rim purple, middle blue and inner archive green) with the most commonly used files in the prime real estate at the outer edge of the disk. This is for the fanatic who wants to squeeze out ever last drop of performance. However, it also has a novice mode, that hides all these techie choices and selects for you. The manual explains quite well what all the options do, but not so much when you would want to use them. The express version gives you no choices.
  • It stores its configuration as a human-readable XML (extensible Markup Language) file X:\Program Files (x86)\Distrix\UltimateDefrag4\UltimateDefrag.xml. This file contains everything to do with configuration, including the definitions of the various numbered scheduled jobs.
  • The manual is excellent, explaining not only the Disktrix program, but how hard disks and defraggers work. It explains what defraggers attempt to do and why.
  • The GUI (Graphic User Interface) is responsive. You can query where various files are or what files are in various clusters, even while it is defragging. It does a number of thing that make it easy to understand just what it is doing.
  • The GUI is compact, easy to understand and easy to read.
  • If you want, you can precisely control the placement of individual files.
  • It, at least psychologically, appears faster than other defraggers, though I have not benchmarked it.
  • It collects the directories and puts them in prime real estate.
  • When it is moving files it shows reads in cyan and writes in yellow. This makes its strategy much clearer. Its strategies are more advanced than the competition and quite fun to watch. I like the way it goes out of its way to keep you up to date with what it is doing. It is not one of those don’-worry-your-pretty-little-head-about-that defraggers.
  • Certain combinations of options will put it into a loop where it shrinks the blue donut stripping off the outer layer and moving it to the inner. It claims it has only a minute to go, but chugs on and on pointlessly. Another time it said there was 0% defragmentation, but it went into a loop moving the same few files back and forth endlessly. It would not even pay attention to the stop button. Until they get this fixed, this is a show-stopper.
  • When the background scheduled task starts it gives an error message complaining about a sharing violation.
  • When the background defragger is running, you cannot launch Ultimate Defrag. It immediately exits without an error message. It should join the background instance and let you interact with it and stop it.
  • When I tried the boot defrag option on a previous version it made my computer unbootable. I was able to recover in an hour or two with my purchased copy of Windows-7. It would not have recovered with the copy of the OS that came with the computer that has no repair facilities. I suspect the problem was an incompatibility with Boot-It Bare Metal boot manager or O & O defragger. When I tried the new version without O&O installed, it said that by D: drive had no files (not true) and exited. It turns out I had no drives configured to defrag at boot time. It should have just bypassed the whole countdown. When I configured some drives for it to defrag at boot time, all went well.
  • Sometimes when you set options, then come back, your options are all scrambled. You have to check all your options prior to each run to make sure they are the way you want.
  • Sometimes the to cluster freezes, and the display gradually fills up with cyan, as if it were moving all the sectors onto one. I trust this is just a display problem. The disk integrity is still intact.
  • If the feature where you click a cluster and see the files in it stops working, click reset pane positions. The problem is the panel where the results are supposed to show up has been closed.
  • You cannot adjust the boot time settings without stopping the defrag. It gives no error message, just refuses to respond.
  • The number of possible tweaking options for the defrag are overwhelming. The documentation tells you what they do, but not when you might want to use them. However, you can just ignore them and click AUTO and still get a very sophisticated algorithm.
  • Disktrix refuses to answer emails until you register the product. They don’t seem to understand that customers don’t register a product until it is working satisfactorily. It is not as if potential customers can bum free support, get the product working, continue to use it and then not pay.
  • When you defrag multiple partitions, it does them in parallel. It should not do that unless the partitions are on separate physical drives. It is much less efficient than doing them sequentially.
  • The menu is confusing. It says simple mode when you are in expert mode and vice versa.
  • When you select files for special placement, it is not just enough to select them. You must drag them to the left panel or click the << button.
  • It has no official command line interface, though it does have a scheduler. I studied how the Disktrix uses the Windows scheduler and deduced that the following kludge should let you trigger one of the predefined scheduled jobs from the command line. It launches DiskTrix in the background. You can’t watch or interact with it.
  • When DiskTrix moved lesser-used files to the inner tracks, it moved them to the absolutely remotest innermost slowest tracks. There is no need to go to this extreme. It just slows down access. This version optionally lets you place them just after the other files.
  • It spends most of its time tweaking the positions of rarely used archive files. It starts it work with the archive files and only after they are done does it work on the important files. This means if you abort the run part way through, it will not have done the most important work. This is a bit like a housewife who starts first cleans the attic when guests are coming.
  • When DiskTrix does a recency defrag, it puts the most recently used files along the outer rim. However, it puts all the free space in the center. Newly created files, the ones you use most, are thus relegated to the sub-prime real estate. It should leave an empty band near the outer rim.
Abelssoft JetDrive
Abelssoft JetDrive
2017.9.1 €30.00 EUR for JetDrive Professional. €50.00 EUR for JetDrive Ultimate.
Last revised/verified: 2017-07-18
  • Runs on XP, W2003, Vista, W2008, W7-32, W7-64, W8-32 and W8-64
  • Extremely fast
  • Pretty Toy Story-like 3D look and feel. They use 3D shaded rendering throughout, even for generated pie charts to show disk usage. Aimed at the naïve user. Fully automatic, almost no confusing options. Needs no configuration. A defragger is not going to do any good unless it is used. This defragger would be good to give to someone who is defragger-phobic. Visually this program stands head and shoulders above the competition. This was quite a surprise for me for a product coming from a company I was unfamiliar with.
  • Your choice of about 30 different colour schemes.
  • It claims to defrag all system files including the MFT,.
  • It is very quick. When you watch it work, you can see is not using the usual flat-footed sequential algorithm. However, they alarm you saying the first defrag could take over 24 hours. They are being overly pessimistic.
  • It gives you choices of seven ways to defrag including by last-access date, by last-modified date, clustering files in the same directory which they call sort by file location and compacting (space consolidation). The various options tell you with animations how relatively how long the defrag will take and what sort of speed improvement you can expect. This is a very good idea. They also tell you the advantages and disadvantages and how often to run each type. Not everyone is a geek. You can also just leave it up to JetDrive to decide.
  • The animated puppy is gone, though you can configure him back. Cute wears thin for me very quickly. The Microsoft paperclip gives me apoplexy when I can’t make it go away.
  • You can ask it to defrag several partitions and walk away. It will do them all and do one reboot unattended if necessary to polish the defrags of all the partitions.
  • Will also defrag the registry (without pruning junk, just compacting deleted entries) and defrag memory. I presume by that they mean internally defragging pagefile.sys. It also deletes junk files before defragging.
  • The deep optimise option will sort directories internally.
  • It internally has a white and black list of SSD drives that can/cannot be safely defragged.
  • They respond to bug reports even before you register.
  • When I installed it, it immediately crashed. However, when I restarted, it picked itself up, apparently unharmed and did not crash again. Apparently I am the only person ever to have that trouble. When I uninstalled and reinstalled it worked fine. It has not happened since.
  • The scrolling display to select what to defrag does not show my T: drive. However, if I select all, it gets defragged anyway.
  • The cluster map is pretty lame. It updates infrequently. It is very coarse. It encodes using only a handful of colours. You can’t tell very much what is it doing. The author said that fancy displays slow down the defrag and most of the time there is no one watching.
  • If you let JetDrive make the decisions, you can start off a defrag with a click or two. However, if you have your own preferred settings, you must reenter them every time.
  • When it reboots to defrag system files, you can’t postpone the reboot. Several times I lost data because I could not put everything to bed fast enough.
  • When you ask it to compact the entire drive, when it completes, the free space is not all in one chunk. It has 12 zones and compacts each zone separately.
  • The legend uses two almost identical shades of green for used and contiguous. I think used means system files, but they don’t document that. They should label it system files and choose a more distinctive colour. If both colours are present, you can tell the difference, but if only one is, you can’t tell which it is.
  • It has no command line interface to let you control it from a bat file.
  • It does tell you much about what is doing. One mysterious activity is optimising which takes it a minute or two before it starts analysing or defragging a partition. What is it doing is freeing up breathing space on the drives, moving data temporarily to other drives if necessary. This greatly speeds up the defrag.
  • It does not even clearly label which partition it is currently defragging.
  • It will not let you just view the cluster map of any given partition. You can only see it during a defrag. It won’t even give a few seconds to admire it when the defrag is finished. It covers it up with dialog boxes. Psychologically it gives the impression it is ashamed of the job it did and it is trying to hide it, like child with a bad report card.
  • It is missing an About box that tells you the installed version and build and Abelssoft does not post the current version on their website.
  • The extra-cost Ultimate version includes a few toys that have nothing to do with defragging.
Diskeeper defragger Condusiv Diskeeper 2011 $69.00 CAD Professional with HyperFast
$344.00 USD Server edition.
In addition there are at least twelve variants, including ones for Windows, VAX (Virtual Address extension) and VMWare.
Last revised/verified: 2012-01-01
Condusiv Diskeeper, formerly Executive Software Diskeeper. Note the spelling Diskeeper not DiskKeeper.
  • Particularly good at speeding up file copies.
  • Defrags, free space, directories, MFT and pagefile.sys
  • Moves dirs to centre of the disk.
  • Has VmWare version called V-locity
  • Very slow. Makes no attempt to position files by last access date.
  • Directory, MFT and pagefile.sys optimisation can only be done at boot time.
  • Boot time defrag can take 15+ hours and is not interruptible.
  • The company has Scientology connections, which may cause trouble if you are in Germany.
  • My computer was in my bedroom and it drove me nuts clicking away in the middle of the night after I installed Diskeeper. The only way I could get it to stop running was to uninstall it.
  • Diskeeper claims that a badly fragmented MFT will double boot time and slow some apps by 50%. Software installs can take 5 times longer.
  • They claim a badly fragmented page file can slow mouse response to 30 seconds. I find that improbable, unless it were a specially constructed pathological case.
  • It claims to improve performance of SSDs by a factor of 6, but I don’t see how it could possibly do that. Position of files on an SSD is supposed to have no effect on speed. Perhaps they use a traditional RAM (Random Access Memory) cache. But what would it do the built-in cache would not? perhaps compression.
Raxco Perfect Disk defragger Raxco Perfect Disk 13.399 $30.00 USD for Home Premium Edition
$42.00 USD for Professional Edition
Last revised/verified: 2012-01-01
  • Specially handles SSDs
  • Runs on XP, W2003, Vista, W2008, W7-32, W7-64, W8-32 and W8-64
  • It tells you exactly what it is doing, which file is it moving out and which file it is moving in.
  • It has 5 defragging options: smart placement (bands), quick defrag only, compress free space, pre shrink (prior to shrinking a partition) and SSD .
  • This defragger targets the niche of very large disks where you must be quick and have to be parsimonious with RAM to get the disk defragged in reasonable time. It is faster than most other defraggers. It is particularly good at improving boot time. It optionally compresses small files. Places most frequently modified (not necessarily most frequently accessed) files near the center of the disk and rarely modified ones near the edges, with the free space in the central band. It will work with only 5% free space.
  • I checked. Its boot time defrag handles absolutely all the metafiles. There is not a single fragmented file left when it is done!
  • IT Pro Magazine gave it their 2008 editor’s choice award. CNET gave it five stars.
  • It unusually good working in the background. It automatically backs off and lets you get work done in the foreground.
  • If you select several partitions and ask it to defrag, it defrags them sequentially.
  • It has something they call OptiWrite that is supposed to prevent fragmentation. They give no details on what it is. It might be a hard disk device driver that modifies Window algorithm for finding free space. It might be something that leaves room at the tail end of growing files.
  • Their online store takes credit cards, PayPal, cheque, money order or wire transfer. They also sell through dealers.
  • If you get into the deeper menus, you can leave bands of empty space for files to grow into.
  • The pro version monitors the SMART (Self-Monitoring, Analysis and Reporting Technology) features of your hard drive to display its temperature and failure rate.
  • The user interface is handsome done in nautical colours. Most of it, however, has nothing whatsoever to do with defragging. I think it would be best if the non-defragging stuff were pruned off into a separate utility. It is just confusing. The way they show fragmented clusters is ingenious.
  • It has a simple command line interface:
    Rem Command line control of Raxco Perfect Disk
    rem /sp means smart placement, /w means wait
    "X:\Program Files\Raxco\PerfectDisk\PDCmd.exe" /sp C: D: E: F: G: /w

    Unfortunately, it gives you no progress information. Clusters disappear for minutes at a time. You can’t tell much about what it is doing or how far it has progressed by looking at the display. You can’t point at a cluster while it is defragging to find out which file it is to learn about how it works.

  • The default colour scheme is well-chosen. I had no problem telling the various classifications apart.
  • The pro version has a non-defragging SSD optimiser, but they give no details on what it does.
  • This is by far the slowest defragger I tested.
  • The trial keeps popping up a nag screen over and over as you work, not just when you start. I don’t think Raxco understands the purpose of a trial. The user is supposed to fall in love with the product and decide they cannot live without it.
  • It gives you little control over how the defragging is done. It is a black box. You get to choose their proprietary Smart Placement option, defrag only or space compression. It uses only last modified time and file extension in deciding placement in its own proprietary way. If you are not a techie, this is a plus. You want it automatic. Deep in the menus you can do some tweaking, but the options amount to minor variants of the built-in ones. You can’t sort by last-access date or last modified date, for example.
  • It does not fully defrag free space, or all the files. You have to run it two or three times to get everything defragged. Raxco claims this is a limitation of the NTFS defrag interface, though I doubt this. It could keep working till it was done, just as its competitors do. Earlier versions often went into an infinite loop, but it has not done that with recent versions. Leaves many files undefragged after a single pass.
  • The user interface using right click, shift-click etc. is efficient for a programmer, but not obvious to a novice. You can must things done by clicking buttons.
  • Raxco claims it holds a patent on the idea of file placement. This is prior art and I can prove it to anyone who needs to break the patent. I posted the idea years ago on BIX (Byte Information Exchange) .
  • When you use the GUI to ask it to defrag several partitions, it defrags them simultaneously. This is not as efficient as defragging them one after the other.
  • It takes two clicks to see the contents of a block (groups of clusters) and you can only view the contents when the defrag is stopped. It should take only one and it should work all the time, with snappy response.
O & O defragger
O & O Professional Defrag
21 $29.00 USD for the single user buynow Take PayPal, credit cards, wire transfer, cheques, money order.
No upgrade discount. This is a problem since they issue new versions at least every year to fix bugs.
$99.00 CAD for the Server edition that lets you defrag an entire LAN (Local Area Network) of machines.

There is also a stripped down free edition.

Last revised/verified: 2017-09-19


  • Specially handles SSDs using TRIM.
  • XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64
  • This is what I originally decided to buy for myself. Five magazines gave it awards.
  • Comes from Germany. You can let it work in the background waking up whenever the system is idle to do a little defragging. You can tune the algorithm to use. You can tune it to sort files alphabetically, to order for fast read access (sorted by last access date, its most logical algorithm in my opinion) or fast write access, or to defrag with minimal resources. It sorts by ascending last access date. Ideally it should sort by descending last access date to put the most frequently accessed files on the fast outer tracks near the beginning of the partition. It supports FAT, FAT32, NTFS , NTFS5, RAID (Redundant Array of Inexpensive Disks) , EFS. Works even on drives larger than a terabyte. It has a scheduler so you can run the defrags unattended. It is clever enough to queue up a request to defrag a partition on the same disk as one being defragged, but will optionally simultaneously defrag a separate physical disk.
  • They take credit cards and PayPal.
  • The Complete/ACCESS algorithm has some nice features:
    • After the first use, it is relatively quick. It moves a few files you have not used in a while to the active end of the disk, creating holes. Then it rapidly slides files down to fill the holes. Often it does not even need to touch the first half of the disk.
    • It optimally organises the files so that the ones you use most often are near the active end of the disk and the ones you hardly ever use are near the beginning, perfectly sorted. No other defragger does this. Others use approximate bands or base the sorting on last modified date rather than last accessed date. This is the key reason I chose O&O for my own use. For this to work properly, you must first turn on last-access date maintenance with the fsutil utility.
    • You can think of it like a house with well-designed many-layered storage for commonly-used items, rarely-used items and an attic. Getting rarely-used files off to the attic reduces clutter.
    • It is equally important to get files used together close to each other on disk as it is to get the fragments of a files. This algorithm does that.
  • It defrags the hibernate file and the registry. It can even defrag the registry without a reboot.
  • The tech people get back to me within hours.
  • You can control it from the command line, e.g.:
    rem defrag with COMPlete ACCess : C: D: E: F: G:
    It works faster and more reliably in this mode. It stops immediately when you ask it to, unlike the GUI interface.
  • In version 12.0 they introduced zones. You can specify three zones and which files belong in each zone. Zone 1 is for files that will not likely change. Zone 2 in for your main data files. Zone 3 is for caches and temporary files. It uses different algorithms to defrag each zone, Zone 1=Complete/Name, Zone 2=Complete/Access and Zone 3=SPACE. This speeds defragging, since three piles are easier to sort than one giant pile of files. It puts programs in the prime real estate of the outer band. I suspect they do this because this is where you get the maximum transfer rate — good for loading programs. The next band is data and the innermost band is rarely used files in the least desirable real estate. You go back and forth between loading programs and processing data. It keeps all the parts of a given program together. It keeps the most active data together. Its file placement is the most intelligent of any defragger However, the overly wide empty space bands means needless extra head movement. You could ameliorate that defect by using a tool like BootIt NG to shrink your partitions to have just the minimum necessary free space.
  • It gives you lots of statistics about the effect of defragging over the last few weeks.


  • I have reported many minor bugs many times. They don’t fix them, just demand huge amounts of irrelevant documentation. This is my personal biggest negative.
  • version 16 is buggy. The command line does not work at all. You have to use one version back.
  • It sometimes crashes if you use the feature to display details about a cluster.
  • If you uninstall version 16, it does not uninstall the boot time defrag.
  • When you install a new version, it will discard most of your configuration settings including your zone filings. The files that control this are not human-editable and presumably may change format between versions. All you can do is take a screenshot of your configuration and re-key it after you install the new version.
  • In version 14+, you must select the drive before you specify your exceptions. If you specify any exceptions for some other drive, they will be quietly ignored.
  • Your configured zones directories will be ignored unless you enable zone processing in a separate menu under: Settings ⇒ Drives ⇒ Advanced.
  • The most annoying feature is version 12 is the way it waits for a minute or two before rebooting. During that time it gives no indication it is busy/waiting.
  • Another feature that annoys me in version 12, is that it displays file maps for all partitions even when it is defragging only one. It even shows maps for partitions not used by Windows. You can’t close any of the unwanted partition displays. This reduces the detail on what it is doing. You can temporarily override it by going into Automatic Settings ⇒ manual.
  • In version 14, Defrag puts the directory entries for each zone contiguously at the head of each zone.
  • It used to be one of the fastest defraggers. It has speeded up a little, but the competition have surpassed it.
  • It in incompatible with Copernic indexer. If you run them both at the same time, O&O will freeze frequently or exhibit strange behaviour. You must unload Copernic from RAM , not just turn off indexing, when  Even this does not stop version 12 from failing to connect with the background engine often. I have found adding a delay after unloading and loading the driver seems to work reasonably well prior to using OODCMD.exe.
    Rem OOR restart O&O Defrag background service
    net stop "O&O Defrag"
    rem give 3 seconds to stop.
    delay 3  /B
    net start "O&O Defrag"
    rem give 3 seconds to get loaded.
    delay 3 /B
    rem -30-
    Unfortunately, neither the GUI nor the command line version will run in safe mode because the background service engine won’t run.
  • When defragging the C: drive, it sometimes seems to restart from the beginning over and over. I have every other application I can think of that might be interfering turned off.
  • When you enter the registration key, it will ask for three fields, your name, your company and your registration key. In my case, to make it work I had to enter my company name in both the name and company field. This is odd given that I gave them both my name and company name during purchase and did not specify if it was an individual or corporate purchase.
  • It seems to be quite slow the first time out. Like most defraggers, it is using the official Windows NTFS defragger interface. On subsequent runs, it is reasonably quick but still slower than some of the competition. I choose to use the Complete/ACCESS algorithm. My machine was noticeably more spritely afterward, particularly program loads.
  • The menu talks about a C:\Windows\Prefetch\layout.ini file to control file layout, but does not document it. If you enable the layout.ini option, the files used by Windows mentioned in layout.ini will be placed near the beginning of the hard disk, in the order specified, to load them faster. The layout.ini file uses UTF-16 encoding. It is a Windows feature for all defraggers, not just O & O. It is just a list of files and directories in the optimal order for bootup.
  • It is adequately fast for a 40 gig hard disk but is too slow for a 250 gig. It is a little too fussy, often going to a great deal of work for a very marginal improvement. I use a series of ever finer defrags, so that if I stop early, I still get some improvement.
  • The shaded colours used in the cluster display are all subtle variations on blue and on top of that appear to be blended for blocks that have a mixture of types inside them. You can’t tell much. Turn off shading to give a clearer viewer. Even then the default colour scheme uses three very similar shades of blue. You can configure a more distinctive colour scheme by double clicking on the colour swatch in the legend. If there is no legend, you can turn it back on again under the View tab.
  • It used to consolidate directory entries together. Now it does not. I wrote a utility called touchdirs part of the FileTimes package, to encourage it, that stamps all directories with the current time as the last access date. If you use COMPLETE/ACCESS this tends to clump all directory entries together. You must use this in conjunction with fsutil to ensure the OS manages file access timestamps. This technique does not work well on the C: drive since Windows won’t give access to its directories to TouchDirs.
  • It does not completely defrag the disk in a single run. See the features matrix below for files it never defrags. It takes many passes, alternating SPACE and ACCESS/COMPLETE and boot STEALTH defrag to get all the files defragged and the space consolidated. This make little practical difference to performance, but is annoying for someone like myself who also uses a defragger for compulsive aesthetic reasons. It may just be that files in use during the defrag bedevil it, but it seems more than that. If, for example, during an ACCESS/COMPLETE run, a there is a locked file in the middle of the slot where a large file would naturally go, it put the file after the locked file, leaving a large space prior to the locked file. It orders the files strictly in last-access order. It seems to me it should fill the hole with small files that would naturally be placed nearby.
  • When using COMPLETE-Access mode, it works on the oldest files first, so if you abort the defrag, you don’t get any improvement. This is analogous to someone who starts his daily housecleaning by cleaning the attic.
  • It is often hard to tell just where it is working on disk. If often appears to be hung when it is moving many small files. There is nothing flickering in the cluster display.
  • Does not defrag metadata (NTFS alternate file forks), UsnJrnl or $bitmap.
  • It will not defrag the page file unless there is a contiguous free space hole big enough to hold it.
  • It does not defrag the MFT . It does not internally tidy or resize the registry, the MFT, the directory etc.
  • When I tried to defrag a FAT32 C: partition in Win2K, it kept rebooting. It could however, defrag a FAT32 D: partition in Win2K.
  • It sometimes turns the machine off, suddenly, with no error message. I was able to correct the problem by running chkdsk (with automatically fix errors checked) on all drives. The problem turned out to be corrupted security descriptors.
  • When running, the ribbon Start button is disabled and when stopped the ribbon stop button is disabled. However, the same button is used for both pause and resume. There is no paused indicator on the ribbon. The screen looks the same whether it is running or paused. The pause button should turn into a resume button when it is paused.
  • Version 11.0+ has a hibernate mode. However, it is a toggle and there is on indicator to tell you the current state. Further, running commands like Launch don’t automatically bring it out of hibernation. It just fails without telling you why.
  • It considers even the old system volume information snapshots (shadow copies) to be exclusively locked. The help files report the bug in Vista that explains why these files cannot be safely defragged. In theory, they could be defragged at boot time. From a performance point of view, this is not a major problem since you rarely use these files.
  • It stores the configuration in a binary file: C:\Users\user\AppData\Local\O&O\O&O Defrag\ocx\ocxdata.bin. This does not appear to include the zone configuration, but I can’t find where it is squirreled away. I looked in every file and in the registry. It might in encrypted or compressed form. This is information is more important than you might think. O&O discards all your settings on every reinstall.
  • With background defrag, a file mysteriously disappeared. I can’t be sure background defrag was the culprit, but I have ever since I have since turned it off.
  • There are three parts to the defrag that work semi-autonomously.
    1. The defrag engine that actually moves files around. It has no user interface.
    2. The GUI that displays how the defrag is going.
    3. The command line interface that names the files as they are moved.
    4. The system tray.
    Each of these four pieces can crash leaving the others running. Much of the problem comes from about 30 seconds lag in the communication or lost messages. You can tell the GUI to display a cell, but the communication delay to the engine and back means it might not respond for 60 seconds, if ever. What they need to do to fix it is provide two communication channels — one for routine traffic and one high priority channel for user commands.
  • When you install, you are best to first, shut down O & O Defrag program, shut down the O & O command line program, shut down the service O & O Defrag with the administrative tools, close the tray icon process with the task manager, uninstall the old version, reboot, close the tray icon process with the task manager again, delete C:\Users\user\AppData\local\O&O\ install the new version and reboot, to make sure you don’t have any problems with the old background engine running.
  • If you ever tested version 11.1 and decided not to upgrade or buy, you may not test version 11.5. Reverting to a previous version after a test can be problematic too. Tech support will give you special OODRM2.exe software to clear things out.
  • If you ever tested version 11.1 and decided not to upgrade or buy, You will need a special temporary evaluation key to test version 11.5.
  • It goes into an endless loop if you edit files in the background while it is working. It needs exclusive use of the machine despite the documentation.
  • I have written them dozens of times about bugs and suggestions for improvement. The usual response is a request for more information, as if I had written them something cryptic in Chinese. I get the distinct impression they are just putting me off. They have never fixed a bug I reported or implemented an improvement no matter how much information I provided them. Part of it may be a language problem. I don’t think many people who work there are very fluent in English.
  • I refused to buy the latest upgrade because it did not address any of the problems I had written them repeatedly about. Further, the things they did change were unimportant.

My comments may sound like utter damnation, but I still consider O&O best of breed, though I if I get some time I will exhaustively retest all the competition to see if I can do better.

Last revised/verified: 2014-05-13
IObit Smart Defrag IOBit Smart Defrag 5.2.0 free and $20.00 USD for the pro version
Last revised/verified: 2016-07-28
This defragger is remarkably good, especially when you consider how cheap it is. This is what I use myself. They will throw in a malware scanner, registry scanner (that found an astounding number of problems), obsolete driver update, privacy scrubber, and system tweaker at no extra charge. Unlike most trialware, it actually fixes the problems it finds. It has beautiful displays. It does boot-time defrags, but not for SSDs. It turns on trimming for your SSD.
  • Works on W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64
  • It does boot time, background(what they call automatic) and scheduled defrags.
  • It use an intelligent quick move algorithm that seems to avoid moving and removing the same clusters, unlike the competition that use mindless brute-force strategies.
  • The user interface is intuitive and straight forward. Everything worked the way I expected it to, with one exception. You must tick off all the drives to defrag, not just select the one you want to defrag. It ignores the one you select and defrags the list with ticks.
  • The GUI looks just as good as any of the commercial competition.
  • It has a clever feature of allowing boot time defrags no more than once a day or once every two days.
  • You can run a defrag only, fast optimise or full optimise depending on how much time you are willing to invest.
It is not perfect, but far from fatally flawed:
  • It is not suitable for SSDs.
  • handles the download for them. The site is a minefield of deception trying to trick you into downloading and installing something that is not IOBit Smart Defrag.
  • You have no control over the algorithm used to place files. For a non-techie, this could be considered an advantage. I think it sorts by last-modify date. It does not do space compression, even when you fully optimise.
  • There is no command line interface.
  • There is no cluster query function to find out what is being stored in each cluster. This makes it hard to figure out what it is thinking.
  • It uses two bands, rather than the traditional three, frequently-used and infrequently-used. It correctly puts most of the frequently used files in the outer prime real estate, but it oddly puts some of them in the centre. I am not sure why. There is no documentation on its strategy on the rationale for it.
  • It does not internally tidy either the registry or the MFT.
  • It used to be extremely slow at analysing disks, but that has been fixed.
Norton Speed Disk Symantec/Norton SpeedDisk part of the Norton Utilities 15 15 $50.00 USD includes 3 licenses.
Norton Utilities 360 is the deluxe version with the same defragger.
Last revised/verified: 2012-01-01
  • W95, W98 and Me and NT, W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64
  • Particularly good at speeding up read access to files.
  • Fast since it does not use the klunky official defrag interface.
  • It can defrag the MFT , pagefile, dirs etc. without a reboot. It places frequently accessed file near the start of the partition.
  • Moves small files into the MFT which gives them faster access and ensures they take up less space. (The downside is the MFT needs more frequent defragging.) It is very simple to run.
  • Puts frequently/infrequently accessed/modified files in separate bands.
  • Places the MFT, then the pagefile, then the directories, then the high access files. Norton’s placement makes more sense to me.
  • The rainbow hued analysis map changes in ways that make sense. Other defraggers seem to have no method to their actions. They appear to just as often be messing up the disk as defragging it.
  • It requires only one session to fully defrag the disk.
  • Norton defragger has been around since the DOS (Disk Operating System) days. It was one of the first.
  • There are no options to configure other than the names of files you want put near the beginning or end of the disk.
  • It has the disturbing quality of redefining how much of each kind of file it has as it progresses.
  • Cannot defrag the first 16 clusters of the MFT .
  • It is quite slow when it defrags small files.
  • Microsoft claims Symantec’s online defrag of the MFT is dangerous. This could just be Microsoft getting huffy over Symantec bypassing its official klutzy defrag interface, or it could represent a true problem. If Microsoft implemented it properly, there would be no need for bypassing it.
  • The defragger is noisier than most, sounding as if it is going to shake your disk to death.
  • Two different sets of utilities all on one CD (Compact Disc), a set. For windows, make sure you manually configure a swap file with Control Panel ⇒ System ⇒ Performance ⇒ Virtual Memory, otherwise SpeedDisk will keep restarting, fearing writes to the temporary swap file. It moves the swap file and directories. However, under  NT, W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64 it does not move directory entries (on FAT partitions) and metadata files (on NTFS partitions). It leaves them where they are, calling them unmovable files, scattered across the drive. To defrag them, you would have to reformat the drive and reload the files, creating all the directory entries first.

Difficult To Defrag Files

There are certain files that are difficult to defrag because the system is using them. They have to be tidied at boot time, before the system starts using them or by locking out a drive to all other programs. These difficult files (often called metadata or locked files.) include: The reboot defrag usually deals well with locked files. You can reduce the number of locked files by shutting down apps just prior to a defrag, in particular ClipMate and Google Desktop. O&O defrag report tells you which files were locked and how badly fragmented they are.

Defragging the Pagefile

Even a premium defragger like O&O won’t necessarily defrag your pagefile (pagefile.sys) or hibernate file (hiberfil.sys). You can fudge it this way. Move the page file to a different drive temporarily, (Control Panel ⇒ System & Maintenance ⇒ System ⇒ Advanced System Settings ⇒ Performance ⇒ Settings ⇒ Advanced Settings ⇒ Advanced ⇒ Virtual Memory ⇒ Change). Then turn off the hibernate feature, (Click Accessories ⇒ right click on Command Prompt, ⇒ click Run as Administrator ⇒ type: powercfg -h off), then reboot. This should cause the two files to disappear off C:. Then defrag and check that there is now a nice big hunk of contiguous free space on C:. Now move the page file back to C:, reboot, then turn hibernation back on. You don’t need to reboot, yet again. The hiberfil.sys should be created immediately. The two files should be allocated in nice contiguous chunks in the free space, with pagefile.sys in the prime real estate.

Alternatively, you can use PageDefrag described above, though it won’t work for Vista.

Feature Comparison Matrix

Defragger Feature Comparison
Disk Area Auslogics Disktrix Paragon O&O Raxco Norton Diskeeper Avanquest PageDefrag
Ordinary files
Order by least recently used
Order by least recently modified
External Registry defrag
Registry internal tidy/prune
External MFT defrag
MFT resize
MFT compact internally
MFT sort internally
$LOGFILE defrag
directory defrag
pagefile defrag
pagefile internal defrag
hibernate defrag
metadata defrag
VSC volume shadow copy restore points
security descriptors

Unfortunately, Paragon, the only defragger to internally compact the MFT, no longer makes defraggers..

Keeping Files Defragged

If you are writing code that involves large random access files, you can keep them defragged between defrag runs if you use this formula whenever your file runs out of space. This is not something you can do as an end user. This is something only programmers can do. The formula gives files a little more space than immediately needed, so 


The life of an SSD will be shortened if you pound it with writes with an ordinary disk defragger. You must use a defragger that treats SSDs specially to avoid writes. There is also no need to position files in any particular spot since they all have equal access time. The defragger is primarily concerned with consolidating free space in one big lump.

The Ideal Defragger

Obviously the ideal defragger should defrag all the files, including the metafiles. It should also optionally internally defrag the MFT putting the most active files together, the pagefile, putting pages for a given job together and the registry, sorting entries alphabetically and compacting out the deadwood.

The ideal defragger should let you trade off speed of defragging vs speed of operating between defrags. The user should not need to be involved with any other details unless he wants to be. Ideally, the defragger needs to know how frequently files are accessed/written (not just how frequently they are opened for read/write), how frequently they change size (gain new fragments) and which files are used together. The OS provides only two primitive approximations, the last-modified-date and the last-accessed-date. The ideal defragger would need to monitor file use between defrags to get a more accurate picture. Properly, the OS should maintain data useful for defraggers.

Real-world defraggers that organise by last-modified-date tend to be fast, since files that need defragmenting tend to be clustered, leaving the other files already in position. Real-world defraggers that organise by last-access-date tend to be slow, but the other apps run faster between defrags. They not only put the most-used files in the prime real-estate, they put files that are used together next to each other.

Disktrix is the only real world defragger that seems to understand the outer rim of the disk is prime real-estate. An ideal defragger should put the most used files there. It should avoid the inner tracks altogether, even for deadwood.

An ideal defragger should leave bands of empty space in places convenient for the OS when nearby files grow. This requires studying the strategies the OS uses to allocate space. It might even be possible to pre-emptively allocate extra space to files guaranteed to grow soon, such as log files. Raxco Perfect Disk has some ability to do this, but only if you are a techie.

Defraggers waste a lot of time sliding a group of files up or down by a few clusters to make room for file that has grown or to close up the space once used by a file that has been deleted. Most of the time this work can be postponed or avoided. The sliding is a lot of work that most of the time makes utterly no difference to performance. Sometimes the clusters have to be shifted to a temporary location then to the final location, which makes the problem even worse. By adding empty space buffer zones cleverly, most of this double shifting can be avoided. If you like to watch the hypnotic display such as those in O & O, you will see that shifts go much faster if there is a fat pocket of free space before the area to be shifted because double shifts are not necessary.

There needs to me some experimentation on the ideal place for a temporary slot when double shifts are needed. I strongly suspect that the first free slot, or the innermost tracks, the strategies used by most real-world defraggers, are strongly sub-optimal.

The defragger should tell you how badly fragmented a drive is so you can tell if it is worthwhile to do a defrag or a boot time defrag/MFT compaction.

It should offer a few options for the hypnotic display including assigning colours for clusters by their ultimate destination, blue near the centre and a smooth spectrum to red near the rim. You would see a rainbow develop as the defrag proceeded. It might assign colours based on how far a cluster is from its ultimate destination — blue for far away in a smooth spectrum to red for in place. The display would gradually turn red as the defrag proceeded, the metaphor being coming home to hearth. See Wavelength for code to generate a rainbow of colours.


I chose O & O defrag for my own  W7-64 system. Though I might flip to Raxco Perfect disk, since it is so much faster and handles all the metafiles.

Defraggers need intact control structures on the disk. If the disks have been corrupted by a system crash or rogue software, running a defragger will only make matters worse. To check for trouble and repair it click Computer ⇒ right click properties for each of your drives ⇒ click tools ⇒ check now. Then reboot. ChkDsk will run twice on each drive, then reboot.

Some people are worried that regular defragging will put extra wear on their disks. Consider that undefragged files put even more wear on disks since the fragments of fragmented files may be accessed tens of thousands of times where it takes only one access to defrag them.

The only reasonably quick and satisfactorily thorough defragger that I know of is Norton SpeedDisk for W95, W98 and Me 9x-FAT partitions. Norton SpeedDisk 5.0 is acceptable for NTFS , but I think with some work it could be speeded up further to handle several small files in a single elevator seek.

I know of no decent ones for OS/2-HPFS or Linux-ext-2 partitions. Perhaps one could be devised that booted under its own mini-OS and defragged by copying from partition to partition handling all the major OS formats. It would then not need to worry about crashing and could do the I/O, including the directory and FAT I/O in massive buffered chunks.

With larger disks, speed becomes more important. Norton is about half the speed of the competition. On the other hand, it gives the best performance improvement.

The Master file table traditionally goes in a band in the middle of a disk, so don’t expect your defragger to compress it down with the other files. This convention was designed to work well if you never defrag. When the disk gets full, this crucial table will me in the middle of the files. You can improve performance if you have dynamic disk partitioning. You can shrink your partitions which will pull the MFT nearer the files on a sparsely populated disk partition. You can grow and shrink the MFT with the fsutil utility.

To write an efficient disk defragger, model how you tidy your apartment, better still, how Martha Stewart tidies her house.

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