The more serious threat comes from undetected data corruptions. The threats described in this page appear here not because they threaten the data itself, but because they threaten its integrity . An obscure error that alters a single byte poses a greater threat to integrity than a meteorite that smashes through the disk drive, for the meteorite can always be detected by the hole in the roof, whereas the obscure error might escape undetected leaving the data corrupted forever. In each case, detection allows the data to be restored from backup. Thus, the regular use of a data integrity tool such as FreeVeracity should be considered as essential a task as backing up.
Operating systems are complicated pieces of software and sometimes contain bugs in file systems.
These bugs tend to arise when an operating system is operated at the limits of its specification, such as when a directory contains the maximum number of files allowed. If the communications line also has a high error rate, the chance of data corruption can be quite high. Unfortunately, the user usually has to set the mode explicitly. Sometimes, when transferring a tree of files directory by directory, it's possible to actually forget to transfer an entire subdirectory. One such problem occurs if the directory on the target machine already contains some files.