The process of files getting corrupted because of some hardware or software failure is called data corruption and this is one of the main problems that 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 get corrupted. You'll find a couple of fail-safes, but often the info is corrupted silently, so neither the particular file system, nor the administrators see anything. Thus, a damaged file will be treated as a standard one and if the hard drive is a part of a RAID, that particular file will be duplicated on all other disk drives. Theoretically, this is for redundancy, but in practice the damage will be worse. Once some file gets damaged, it will be partly or entirely unreadable, which means that a text file will not be readable, an image file will display a random blend of colors in case it opens at all and an archive shall be impossible to unpack, so you risk sacrificing your site content. Although the most widespread server file systems include various checks, they frequently fail to find some problem early enough or require a long period of time to check all of the files and the hosting server will not be functional for the time being.