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Scanning for File System Data Corruption

Due to the complexity of the file system used on modern PCs, there is always the risk that file system errors and corruption will develop in the logical structures that control the disk. Most of the time, these problems are caused by buggy software, bad drivers, power failures or human error. Rarely, they are the result of actual hardware problems with the PC.

File system integrity problems can on occasion lead to data loss. It is important that any problems be caught as soon as possible, to minimize the chances of extensive damage. Fortunately, checking for file system problems is very quick and easy to do. Since it is easy to do and important, and can be set up to run automatically by program schedulers, I recommend that file systems be scanned for errors on a daily basis. You can do it less often, but you increase the chances of problems mushrooming.

The two most popular tools for analyzing file system problems are probably those from Microsoft and Symantec's Norton Utilities. (In fact, the Microsoft tools are watered-down, licensed versions of Norton Disk Doctor). The Norton tool is better, but the Microsoft tool is free. Both will do the job just fine, in my experience. They can be run from the command line in a DOS environment (by running "SCANDISK" for Microsoft, or "NDD" for Norton), or accessed by right-clicking on a drive icon and selecting "Properties" under Windows 95.

Tip: These tools will detect hard disk read errors if you ask them to, after they check for and correct any file system problems. Detecting file system problems, and detecting hard disk read errors, are really two different things, despite the fact that they are being done by the same utility program.

Warning: The DOS "CHKDSK" utility is a much older disk error-checking program. It is still included in DOS (and Windows 95) but I find that it is at times unreliable. It is not as robust as SCANDISK or Norton Disk Doctor, and I don't recommend its use. For Windows NT, however, CHKDSK is the only included tool, however I believe there it has been improved over the DOS version.

Typical problems such as a small number of lost clusters on a disk volume, are nothing to be concerned about. These are usually file fragments left over when a program crashes, or when there is a power failure. Other problems, such as file allocation errors or cross-linked files, happen more rarely. If these are happening a great deal, it may be a sign of a problem such as a hardware failure, too-fast timing on a hard disk, or even virus infestation.

Warning: Always use the proper tool for your operating system. Do not use old versions of SCANDISK etc. on newer systems running Windows 95, for example. And make sure that if you are using FAT32, that you use tools that are modern enough to recognize the newer file system (or you will make a big mess of your hard disk!)

Next: Detecting Hard Disk Read Errors

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