Diagnose hard-drive disaster

Without warning, your Mac is on the fritz. System crashes occur every time you click your mouse, or worse, your Mac displays a gray screen at startup. You feel panic. Is your hard drive dying and taking your data with it? Maybe not. There are a few tricks you can try that may save the day. Sit down. Take a deep breath. Read on.

Why good drives go bad

All your data is written on and read from your drive’s magnetic media surface. Depending on the age and quality of the drive—and how often it’s used—bits of media may flake off this surface. It doesn’t happen frequently, but when it does, you can no longer write to that segment or block, and you lose the data on it. Mac OS X offers some protection: if it can’t access a segment, it will automatically map out that block (make it unusable). This feature isn’t fail-safe, though—a block may go bad after your Mac has written something to it.

Drives can also suffer mechanical failure. As a drive reads and writes data, the platter spins and the drive head moves. If one of these parts fails or the power supply stops working, you have a dead drive.

Look for symptoms

Drives don’t always fail catastrophically. For instance, when a block goes bad, you may still be able to read from it occasionally. Likewise, a stuck drive may start to spin after it’s been on for a few minutes. Consider yourself lucky—there’s still time to save your data.

You typically discover bad blocks when reading from or writing to them, but the symptoms depend largely on what that block contains. If it’s a document, it might fail to open. If it’s core system software, system crashes may occur (although it can be hard to tell whether that’s due to media damage or software problems such as a corrupt directory).

Other clues that there’s a hardware problem include frequent crashes within a variety of programs and unusually long application-launch times. Strange sounds can also tip you off; a drive that’s on its last legs might make disquieting grinding or clicking noises. If a drive is dead, you’ll hear nothing but eerie silence.

Back up and recover

If your drive exhibits symptoms, try and save all critical files that you haven’t already backed up—to DVD, a second drive, or other media. It’s easiest to drag and drop files via the Finder. Don’t overwrite an existing backup—you may end up replacing a good backup with a corrupted one. And back up immediately. If you do anything else, data recovery may become impossible.

If the defective drive is the one you use for startup, you may have trouble booting up from it. In this situation, it’s best to start up from another bootable hard drive rather than a system CD or DVD. Using a hard drive will make it easier for you to recover files and choose which disk-repair utility to launch, because you retain Finder access. To boot from an external drive, you first need to install OS X on it. (If you have an iPod, you may be able to set it up as a bootable drive; see The Return of iPod Booting.)

Connect the external drive and then restart your computer while holding down the option key. Use the arrow keys to select the external drive in the Startup Manager screen that appears. Hopefully, the problem drive will mount as a secondary disk and you can copy data from it. If it doesn’t, launch Disk Utility (/Applications/Utilities), select the drive (provided it’s listed), and click on the Mount button.

No luck? You may be able to save files through data-recovery software. Prosoft Engineering’s $100 Data Rescue II (   ) can locate and recover files on a damaged drive, even when the drive itself is beyond repair. The process can take a while and it may or may not work, depending upon the nature of the damage, but it’s worth a shot.

Test your drive

It’s time to determine the cause of your problems—and whether you can solve them.

Get SMART Self-Monitoring Analysis and Reporting Technology (SMART) keeps tabs on a hard drive (primarily media problems), and most current drives support it. To check a drive’s SMART status, launch Disk Utility. Select the drive (not one of the partitioned volumes listed underneath), and look for its SMART status at the bottom of the window. A Verified status means that the drive passed its SMART tests. Not Supported indicates that your drive does not permit SMART testing. An About To Fail message is a sign that it’s time to get a new drive.

Run Apple Hardware Test This test can check for problems with various hardware components, including your drive. How you access this software varies on different Macs. For recent models, insert the Mac OS X install disc, restart, and hold down the option key (on PowerPC Macs) or the D key (on Intel Macs). Click on the Apple Hardware Test icon when it appears. In the Hardware Tests tab, click on Quick Test (PowerPC) or Test (Intel). Unless the test reports a problem with storage, your drive is probably fine.

Try TechTool Pro Micromat’s $98 TechTool Pro 4.5.1 can also check for hardware problems, including bad blocks. ( Check compatibility information.) Select Tests from the toolbar and then click on the Drives tab. Click on the Show Drive Tests disclosure triangle to reveal the different tests, and select Surface Scan from the list. This test can find and report the number of bad blocks on a drive, but it can’t repair them. If the utility finds bad blocks, your drive might be on the way out (for more on this, continue on to “Diagnosis: Hardware Failure”).

Repair the software

If your problem drive passes these hardware tests, it probably has a corrupt directory rather than physical damage. Try Disk Utility’s First Aid or an application such as Alsoft’s $80 DiskWarrior 3.0.3 (   ). (At press time, DiskWarrior wasn’t compatible with Intel Macs.)

To repair your drive using First Aid, launch Disk Utility and select the troubled volume. In the First Aid tab, click on the Repair Disk button. If you’re repairing your startup disk, you’ll need to boot from a different volume, such as a Mac OS X installation disc. (For more about Disk Utility repair, see OS X First Aid.)

If Disk Utility detects and fixes the problems, hopefully you’re home free. If it fails to detect any problems, reinstall Mac OS X using the Installer utility’s Archive & Install option. If DiskUtility reports problems but can’t fix them, try reformatting, which erases all data, using its Partition command—the preferable way to reformat a drive when bad blocks aren’t an issue. Launch DiskUtility, select the drive, and, in the Partition tab, click on Partition.

Diagnosis: hardware failure

What if all your software repair attempts fail or your tests indicate a hardware problem? Here are the most common courses of action to take (for a more desperate approach, see “Last Resorts”).

Reformat the Drive If the drive is still responsive, you may be able to reformat it. Just make sure any bad blocks are mapped out. Launch Disk Utility, select the drive, and, in the Erase tab, click on the Security Options button. Select Zero Out Data (see screenshot). Click on OK and then on Erase. Warning: If reformatting works, your success may be short-lived. Symptoms will return if new blocks turn bad.

Ditch It Sadly, discarding a drive is a common way of dealing with drive failures. If your drive is under warranty, contact the maker; otherwise, you’ll need to replace it. At this point, drive repair is often impossible.

Last resorts

If all efforts to save your hard drive have failed and you still have critical unrecovered files, here are some last-ditch options:

1. Contact a Pro Services such as DriveSavers may be able to recover data, using techniques that aren’t available to laypeople. (Contact such a company before attempting to reformat the drive). The downside is the cost. Fees in excess of $2,000 are not unusual.

2. Try Extreme Means Don’t want to shell out for professional help? You may be able to unstick the drive long enough to recover your data. Make like the Fonz and try giving the drive a medium-size whack (when it’s not running). Alternatively, try putting it in the freezer. (Heat expansion can cause a drive to get stuck; the cold air might contract it again.) Remember, these are last-resort measures. Try them only if you’re planning to trash the drive anyway.— Ted Landau and Christopher Breen

[ Senior Contributor Ted Landau is the founder of MacFixIt, where he writes a regular column. ]

Saved by Zero: Disk Utility’s reformatting option checks for bad blocks and maps them out.

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