RUNNING DIAGNOSTIC ON MAC OS X

The OS auto-defrags on the fly for files less than 10 (maybe 20) MB.
It will periodically (daily, weekly, and monthly) run routines that "clean up" the disk.
If you open Disk Utility and select the disk, it will display the S.M.A.R.T. status of the drive.

I have never run any maintenance program on my Macs (5 of them) and I've never had any problems with updates, upgrades or crashes.

No, you really don't need to run diagnostics and analysis software. I've gotten by for 7 years with OS X without ever using Techtool Pro.

I have run DiskWarrior 2 or 3 times during that time frame and fixed some reported issues, but, frankly, I don't know that it was necessary because I wasn't experiencing any issues before or after I ran DW so I can't really that it fixed anything that was observable.

I agree; OS X is pretty much maintenance free; but every couple of months, or more often with heavy use, I use Disc Warrior to rebuild the disk directories; it seems to speed things up a bit, and its a good tool to have on hand if any problems crop up.

See it [here|www.alsoft.com].

The built-in disk utility will check the disk for errors and also check the files for proper permissions and repair them, if necessary. It's similar to the windows diskcheck and goes one better with the permissions. The underlying OS is BSD, a Unix-like OS that does not need defragging as does windows systems. It takes care of itself. I have never defragged a Mac OS and my 3 computers all work fine.
The file system is what is called Journaled. It keeps tabs on what's going on so that if you force a shutdown or lose power on a desktop, when you restart you do not suffer the long tedious repair that windows requires. The Journal contains enough info to quickly repair the file system as you boot. It takes less than a minute. Also, a disk check is forced on boot on a regular basis, so occasionally when you turn on the computer and wonder why it's taking longer than usual, it's just checking itself. This is standard for most Unix systems.
If errors are found and corrected, you will find the junk file in the trash, labeled recovered files.
Techtool is OK. If you join .mac, it's free.

you can copy/paste to the terminal and do maintenance on your Mac.

The Terminal way
Using your Admin account, you can execute all three maintenance scripts at once, as follows:
1. Launch Terminal, in the Macintosh HD > Applications > Utilities folder.
2. At the Terminal prompt, type the following, exactly as written:
3. sudo periodic daily weekly monthly

4. Press Return.
5. Type your Admin password when prompted, then press Return.
All three scripts will run in sequence. There is no visual feedback while the scripts execute. You will know they are completed when the Terminal prompt returns.
You can also run the scripts individually. For example, to run just the daily script, you would type the command:
sudo periodic daily
in step 2 above.
Determining when the maintenance scripts last ran
You can execute a Terminal command to quickly check the date and time stamps of the log files associated with each maintenance script. This indicates when the scripts' own logs were last updated, and hence when the scripts were last executed.
1. Launch Terminal, in the Macintosh HD > Applications > Utilities folder.
2. At the Terminal prompt, type the following, exactly as written:
3. ls -al /var/log/*.out
4. Press Return.
You will see output similar to the following:
-rw-r--r-- 1 root wheel 467984 8 May 10:40 /var/log/daily.out
-rw-r--r-- 1 root wheel 1258 8 May 10:43 /var/log/monthly.out
-rw-r--r-- 1 root wheel 198378 8 May 10:43 /var/log/weekly.out
In this example, the scripts last ran on 8 May of the current year, between 10:40 and 10:43 local time. The date and time stamps in the example are the result of running the scripts manually using Terminal. If the scripts were run automatically on their default schedule, their date stamps would vary and their time stamps would indicate executions between 03:15 and 05:30 hours.

Also, take a look at the Apple Hardware Test .