So it's still a good idea to use a disk utility occasionally, especially whenever you experience unexplained problems, crashes or failures to open items. If you have drives that aren't journaled, you should still do this on a regular (close to monthly) basis. Journaled drives, however, can be checked less frequently. You can try Disk Utility's Verify Disk and Repair Disk features or a third-party utility such as Micromat's TechTool Pro, Prosoft's Drive Genius, or Alsoft's DiskWarrior, all of which cost around US$100.
These tools essentially work by comparing a drive's directory with its actual contents , also called verifying or examining the disk. If problems are found, the utilities can attempt to repair the directory.
The extent to which they are successful depends on the format of the disk, the extent of the damage and the utility being used. In general, third-party utilities tend to be somewhat more successful than Disk Utility in recovering severely damaged directories, though your mileage may vary.
Generally, Disk Utility (found in /Applications/Utilities) is the first stop for checking for hard drive issues because it is freely available and relatively easy to use for identifying and resolving most problems. To verify or repair a drive's directory structures, select the drive from Disk Utility's list box, click the First Aid tab, and click the Verify Disk or Repair Disk button.
When you repair a disk, Disk Utility will first verify the disk and then attempt to repair the directory information if it finds problems.
Note: If you are comfortable working from the command line, you can also boot a Mac into single-user mode and use the Unix fsck command, though this is more commonly used as a troubleshooting option if a Mac's hard drive is so corrupted that it can't boot successfully.
The same functionality is available in Disk Utility, which is generally easier and safer for many users, as fsck 's options and single-user mode provide unrestricted access to a Mac's file system.
Then there are the physical components to any hard drive. These include the spinning magnetic disks (known as platters) that hold data, the read/write heads that scan and access those platters, the drive motors, the cache RAM chips that speed up data access, and the chips that tell the drive how to function and interact with the other components of a computer. A failure in any of these physical components can lead to problems much more serious than disk directory problems.