The process of files being damaged owing to some hardware or software failure is known as data corruption and this is among the main problems that Internet hosting companies face as the larger a hard drive is and the more information is stored on it, the more likely it is for data to be corrupted. There're a couple of fail-safes, still often the information is corrupted silently, so neither the file system, nor the admins notice a thing. Thus, a bad file will be handled as a standard one and if the HDD is a part of a RAID, the file will be duplicated on all other disk drives. Theoretically, this is done for redundancy, but in reality the damage will be even worse. The moment a given file gets corrupted, it will be partially or fully unreadable, so a text file will not be readable, an image file will present a random mix of colors if it opens at all and an archive will be impossible to unpack, so you risk losing your website content. Although the most widely used server file systems have various checks, they often fail to detect some problem early enough or require a long period of time to be able to check all files and the web hosting server will not be functional in the meantime.