The process of files being damaged resulting from some hardware or software failure is referred to as data corruption and this is one of the main problems that web hosting companies face because the larger a hard disk drive is and the more data is placed on it, the more likely it is for data to become corrupted. You'll find various fail-safes, still often the info becomes damaged silently, so neither the particular file system, nor the administrators notice anything. Consequently, a bad file will be treated as a standard one and if the hard disk drive is a part of a RAID, that particular file will be copied on all other disk drives. Theoretically, this is for redundancy, but in reality the damage will get even worse. The moment some file gets damaged, it will be partly or fully unreadable, so a text file will no longer be readable, an image file will show a random combination of colors in case it opens at all and an archive will be impossible to unpack, so you risk sacrificing your content. Although the most widespread server file systems include various checks, they are likely to fail to detect some problem early enough or require an extensive period of time to be able to check all files and the web server will not be functional in the meantime.
