Miscellaneous Ramblings

DiskWarrior 3: The One Disk Utility Every Mac User Should Have

Charles Moore - 2006.05.30 - Tip Jar

When I'm asked what is the best Mac disk maintenance and repair tool, my advice is that you really should have more than one - but If it has to be just one, my vote goes to Alsoft's venerable and superb DiskWarrior. I've been a DiskWarrior fan since back in 1998 when it first arrived on the scene.

DiskWarrior has always been essentially a one-trick pony, but it does that trick exceedingly well, which is to diagnose and repair disk directory damage cleanly, efficiently, and effectively. (The OS X version of the program can also be configured to check hard drives for media and or mechanical malfunction as well - see below.)

Directory Damage

Disk directories are the area of a hard disk that the Mac OS uses to "map" all the information stored on the drive so that the Finder can find it. The directory records the number, names, locations, and sizes of all files and folders stored on the disk. If any of this information becomes corrupted - incorrectly updated or not updated - the directory is considered to be damaged.


Quite a lot of cumulative directory damage can occur without being immediately noticeable to the user, and this is especially likely to happen if the computer crashes, suffers a kernel panic, or encounters another problem requiring a force restart or reset without properly shutting down. Poorly written programs can also write data erroneously into the portion of the disk reserved for directories.

If directory damage is left unresolved, it tends to become worse and could eventually result in permanent data loss and/or system instability.

DiskWarrior doesn't only rebuild the directory; it also optimizes it for performance by defragmenting it and packing nodes, making the physical order equal to the linked (logical) order. Packing combines nodes that are not full so you end up with fewer nodes.

before and afterUsers can also create a graph (right) that indicates how severely the directory is fragmented - not just the number of fragments, but a visual depiction of the distance each fragment is out of place. Each part (node) is assigned a color along a gradient between white and dark blue, depending upon the optimization of its position. The more distant a fragment is from its optimized position, the greater difference between the color of the fragment and the color of the same position on the example graph.

Tiger Needs DW 3.0.3

The old DiskWarrior 2.x for the classic Mac OS served me extremely well, even into the OS X era, although it took it's time - an very long time - working its way through the tens of thousands of tiny Unix files on a disk or partition with OS X installed. I still highly recommend it for machines running the classic Mac OS. However, DW 2 will no longer support disks with OS 10.4.x "Tiger" installed.

In order to run DiskWarrior while started from Mac OS X 10.4.x you will need DiskWarrior version 3.0.3. Alsoft reassures us that earlier versions of DiskWarrior (including up to version 3.0.2 for OS X), while not compatible with Tiger, will not harm your disk, but attempting to rebuild a disk with one of the earlier versions while started from Tiger will result in an error stating that a "Mac OS Services" failure occurred.

DiskWarrior and OS X

Happily, DiskWarrior 3.0.3 is a lot faster on OS X volumes than old DiskWarrior 2.x was, works with both Mac OS Standard (HFS) or Mac OS Extended (HFS Plus) formatted disks, and on any Mac with G3 or better PowerPC (non-Intel) processor (G3, G4, or G5) with built-in FireWire and a minimum of 256 MB RAM (384 MB or more is recommended) that can start up and run from the DiskWarrior CD, regardless of what operating system is installed on the disk to be rebuilt.

The computer must also have the latest firmware updates installed. The disk to be rebuilt must be locally connected, not write-protected, have a valid partition map, and have a case-insensitive directory. OS X certainly is a lot more picky about such things than the laid back old classic Mac OS was.

If you plan to rebuild the directory on your startup disk, you need to start up from another disk capable of starting up in Mac OS X 10.2.1 through 10.4.x, such as the DiskWarrior CD, although I'm more inclined to use a copy of DW installed on my external FireWire hard drive.

Incidentally, version 2.1 of DiskWarrior is also bundled on the DiskWarrior 3.0.3 CD. It supports 68020 Macs or better when started from Mac OS 7.1 through 9.x.

Either version of DiskWarrior repairs any supported disk no matter which version of the Mac OS is installed on the disk being repaired.

Not for Intel (Yet)

The latest DiskWarrior CD (revision 39) is now shipping with DiskWarrior 3.0.3 and can start any PowerPC-based (non-Intel) Mac models introduced as of 2005.10.19. The last generation iBook models introduced on 2005.07.26, the iMac G5 (with built-in iSight) models introduced on 2005.10.12, and the Power Mac G5 (dual-core) and PowerBook models introduced on 2005.10.19 can be started from the current CD.

If you want to enable DiskWarrior's automatic hardware monitoring feature that I mentioned above, you will need to install DiskWarrior on your Mac, which must be capable of running Mac OS X 10.2.1 through 10.4.x and have at least 256 MB RAM (IMHO anyone using OS X with less than 512 MB of RAM installed is a glutton for punishment). Using DiskWarrior for its primary function of disk directory diagnostics and repair works fine from the DiskWarrior CD, although booting, as with any CD bootup, takes a long time.

What DW Does

Unlike some disk utilities, DiskWarrior doesn't attempt to patch detected errors in the disk directory database. Instead it uses a powerful scavenger engine to retrieve data from the existing directory, determine whether it is reliable or not, and then creates a fresh, new directory from all reliable data found. DiskWarrior rebuilds the directory, fixes errors, eliminates problems errors have caused, and recovers lost files - and then fixes any issues detected with the master and alternate master directory blocks, volume headers (HFS Plus), volume bitmaps, catalog trees, and extents trees.

Even if you have no idea what any of that means, DiskWarrior, in the best Macintosh tradition, "just works" through a user-friendly, easy to understand graphical user interface.

If you're familiar with DiskWarrior for the classic Mac OS, you should feel quite at home in the OS X version, although there are some differences. It's still elegant, simple, user-friendly, and, as noted, significantly faster on those pesky OS X volumes, although it still takes time to work its way through all those little bitty files. It does require password entry at steps of the process, while the classic version doesn't - but that's OS X for you.

DiskWarriorDiskWarrior ships on a bootable CD that has a special version of the OS X System Folder licensed from Apple that does not contain a Finder. Instead, DiskWarrior has a Finder substitute called DiskWarrior Preview that allows you to preview repairs to your disk directory. When you are booted from the DiskWarrior CD, you can launch DiskWarrior Preview by clicking the Preview button in the DiskWarrior Report window.

When you start up DiskWarrior 3, an interface window will appear (right) asking you to choose a volume from a popup menu and then click the Rebuild button to initiate the rebuild process. If you click the "advanced" button, you will also be provided with extended information about your disk.

You will be asked to enter your administrator password, and the process will proceed, which you can monitor in the progress bars that will appear.

Once DiskWarrior has examined the old directory and constructed a new one, it displays a report (left) showing any problems found and indicating whether they were repaired successfully or not. You then have the option to either replace the old directory with the new one or cancel the operation, in which case everything will be left as it had been.

Before writing a new directory, DiskWarrior will prompt you to enter your administrator password again, and compares the old and new directories before doing the write.

The New Directory

Whenever there is enough free disk space to write temporary replacement directories, DiskWarrior uses a fail-safe write to disk mode. However, I've used it more often than not on volumes without enough free space left for fail-safe write to work, and I've experienced no problems. If there is room, DiskWarrior will write a rebuilt, optimized replacement directory in the free space where the original directory is located; it then tells the computer to use this replacement directory instead of the original one.

The reason for the second copy is to locate the directory as close to the head of the disk as possible. The replacement directory is written and actuated before the original one is deleted, ensuring that there is no risk of ending up with an unreadable disk should the process be interrupted.

If there is not enough free space on the drive to hold the replacement directory, a dialog will appear warning that an interruption during the write-over phase could result in data loss. You then have the option of proceeding or aborting. With laptop computers, of course, there is extremely small likelihood of power loss interruptions because the AC adapter power supply is backed up by the computer's internal battery.

New in DW 3

DiskWarrior supports the SMART self-diagnostic technology on ATA drives that incorporate it and can be configured to automatically check devices for mechanical malfunctions. By activating the automatic hardware diagnostics, DiskWarrior will initiate internal diagnostic routines built into your drive as often as you specify.

Alsoft notes that DiskWarrior 3.x is not a simple port of version 2 to OS X. Extensive changes had to be made to transform DiskWarrior into an OS X native application ("Carbon" ports are not possible for utilities that address hardware). DiskWarrior 3 supports file journaling, Mac OS X RAID, offers full Unicode support, conforms to Apple's security standard, uses the OS X native memory model, and is capable of rebuilding directories as large as 2,000 gigabytes (two terabytes).

The One to Have

DiskWarrior is the disk tool to have if you're only having one, and there are really no negatives I can think of other than that it's a bit pricey, but not extraordinarily so for this type of software.

The obvious use for DiskWarrior is when you suspect directory damage on one of your disks. Directory damage can result in the disk not mounting (not appearing on the desktop when the computer is started), missing files or folders, an inability to move or copy files, or crashes when you attempt to open a file.

However, it's even better to use DiskWarrior for preventative maintenance of your disks, catching damage that may be there before it becomes noticeable in regular use and preventing any such damage from escalating.

Other than the modest amount of time it takes, there is really no downside to letting DiskWarrior rebuild your disk directory on a periodic basis - and since new directories DiskWarrior creates are also optimized for maximum directory performance, you can realize speedier disk performance.

DiskWarrior 3.0.3 for Mac OS X 10.2-10.4 (which includes DiskWarrior 2.1 for Mac OS 7.1-9.2.2) sells for $79.95. If you are a registered user of DiskWarrior 2.1 or earlier, you can order the DiskWarrior 3.0.3 upgrade for $39.95 plus $7.95 shipping and handling.

DiskWarrior Features

  • Uses directory data to quickly rebuild the directory structure
  • Eliminates risk of losing access to files other disk "repair" utilities attempt to fix the directory by patching the directory structure and risk deleting sections of the directory
  • Scavenges directory to find all salvageable file and folder data, even data contained in damaged nodes
  • Eliminates unseen directory errors, preventing minor directory errors from escalating into major problems
  • Recovers lost files and folders
  • Optimizes directory for maximum directory performance, speeding up overall disk performance
  • Monitors drive hardware for potential drive failure
  • Verification of replacement directory ensures data integrity
  • Comparison of original directory with replacement directory tells you which files and folders may have been affected by directory damage
  • Patented preview feature to view what the disk will look like after the directory is rebuilt, allowing you to view files and folders before any directory changes are written to disk
  • Repairs damaged boot blocks and blesses the system folder to ensure that the computer will start from the repaired disk
  • Checks custom icon files for corruption, eliminating a common cause of system crashes
  • Repairs problems with wrapper volume System files caused when HFS Plus disks are initialized under Mac OS 9.0 - 9.0.4
  • Safely permits interruptions of any kind, including power outages
  • Advanced "Verify Reads and Writes" technology protects your data
  • Supports bad block sparing software
  • Supports file journaling (Mac OS X 10.2.2 or later)

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Charles Moore has been a freelance journalist since 1987 and began writing for Mac websites in May 1998. His The Road Warrior column was a regular feature on MacOpinion, he is news editor at Applelinks.com and a columnist at MacPrices.net. If you find his articles helpful, please consider making a donation to his tip jar.

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