How DiskWarrior works

[e.mkeene]

To clarify DiskWarrior for those who may be thoroughly confused:

Imagine having a 300 page book bound in a looseleaf binder. You drop 
the binder and the rings pop open scattering the 300 pages on the 
ground. A 30 mile an hour wind is blowing gently and all of the pages 
go flying. Originally, the book had a table of contents and an index. 
So if you manage to find all the pages including those and assuming all 
the pages are numbered, it will take some time but you can reassemble 
the book with no harm done except for the lost time.

But suppose instead you found everything except the table of contents. 
Well, you think to yourself, I still have the index so it should be no 
problem to put it back together. After about 30 minutes, you finally 
admit the futility of using an index to reassemble a disassembled book. 
At this point, you are faced with the task of reading each page and 
hoping you knew enough about the book before it came apart that you can 
sort of begin putting it together in small sections.

After a few hours, you finally decide, you will either have to find 
another copy of the book, a copy of the table of contents, throw the 
book away, buy another copy or forget you ever owned it.

That is what happens to your hard drive. When you have been using it a 
while and adding and deleting or modifying files frequently, the pages 
get all mixed up on the  drive. But the drive has both a table of 
contents and an index of sorts. Additionally, it has a database folder 
that keeps track of all the changes and where all the pieces have been 
put each time a change of any sort occurs. So when you open a file, 
these 3 elements scramble to collect the various pieces and reassemble 
it for you.

When something happens to your directory, a crash or two, improper 
saving or shutting down, software clashes, dirty electricity, 
electrical brownouts, etc., bits of the directory or database can get 
damaged or corrupted. Sometimes, the damage will be incomplete and the 
files will still open correctly. Other times, they will have missing 
info, sometimes, they will be toast.

Most utilities, including Norton, simply try to make the pieces fit the 
existing directory and database whether they do or not. Many times, the 
guessing this entails will be close enough and everything looks good 
and works again, for a while. But enough of this forced patching 
eventually takes its toll and things don't work anymore.

DiskWarrior was the first and to my knowledge is still the only utility 
that uses a different method. It simply uses the information left in 
the directory and database to check for errors first. Once it confirms 
how much of that data is correct, it then writes an entirely new 
directory (table of contents, index and database).

Once that task is completed, it then gives you a summary of what it had 
to do. How many errors were fixable, how many were not fixable, usually 
it also names the files in question, etc. Then it presents you with the 
original directory and a copy of the new directory it has created. In 
DW 3, it lines the files up side by side so you can then open each file 
in both directories and check for errors, losses, etc. When you are 
satisfied no files are lost, you can tell DW to REPLACE the old 
directory with the newly written directory.

If  you find missing files, you can abort the process, back up the 
files that are in question or the entire disk, and then rewrite the 
directory. On occasion, I have had DW report errors it could not 
resolve but when I inspected the files, I couldn't find any lost data.

While prudence always dictates backing up your files prior to using any 
utilites, I have to admit that like many users, I am not always careful 
to do that. With DW, I have never lost any data and I even know people 
who have been able to recover files or drives that resisted all other 
efforts to repair or recover  them. One of my friends is a network 
admin and he regularly saves his company huge amounts of money using DW 
to repair directories and save the cost of using DriveSavers to recover 
the data.

One rule I do obey religiously-I ALWAYS BACKUP BEFORE OPTIMIZING or 
clean installing or installing a new OS. Hope this helps to clear up 
the fog for any newbies lurking on the edges or caught in the fog.

Mac Computer Show and Sale December 13th
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