The process of files being corrupted as a result of some hardware or software failure is known as data corruption and this is among the main problems that hosting companies face since the larger a hard disk is and the more info is filed on it, the much more likely it is for data to get corrupted. You'll find several fail-safes, still often the info is corrupted silently, so neither the file system, nor the administrators detect anything. As a result, a corrupted file will be handled as a good one and if the hard disk is a part of a RAID, that particular file will be copied on all other disk drives. In principle, this is done for redundancy, but in reality the damage will be worse. Once a file gets damaged, it will be partly or fully unreadable, therefore a text file will no longer be readable, an image file will show a random mix of colors in case it opens at all and an archive will be impossible to unpack, so you risk sacrificing your website content. Although the most commonly used server file systems have various checks, they are likely to fail to discover some problem early enough or require a long amount of time to be able to check all of the files and the hosting server will not be operational in the meantime.