Protection

• When information is stored in a computer system, we want to keep it safe from physical damage (reliability) and improper access (protection).
• Reliability is generally provided by duplicate copies of files (copy disk files to tape).
• File systems can be damaged by hardware problems (such as errors in reading or writing), power surges or failures, head crashes, dirt, temperature extremes, and vandalism. Files may be deleted accidentally. Bugs in the file-system software can also cause file contents to be lost.