The process of files getting corrupted caused by some hardware or software failure is known as data corruption and this is one of the main problems that Internet hosting companies face since the larger a hard disk is and the more information is kept on it, the much more likely it is for data to become corrupted. You'll find various fail-safes, but often the data becomes corrupted silently, so neither the file system, nor the administrators notice anything. As a result, a corrupted file will be treated as a regular one and if the HDD is part of a RAID, that file will be copied on all other disk drives. Theoretically, this is done for redundancy, but in reality the damage will get even worse. When a given file gets damaged, it will be partially or entirely unreadable, so a text file will no longer be readable, an image file will display a random mix of colors if it opens at all and an archive will be impossible to unpack, and you risk sacrificing your content. Although the most commonly used server file systems feature various checks, they are likely to fail to find some problem early enough or require a vast period of time to be able to check all the files and the web hosting server will not be functional for the time being.