The process of files being damaged as a result of some hardware or software failure is referred to as data corruption and this is one of the main problems which hosting companies face because the larger a hard drive is and the more information is placed on it, the more likely it is for data to get corrupted. You will find a couple of fail-safes, but often the data gets damaged silently, so neither the file system, nor the administrators see anything. Because of this, a bad file will be handled as a regular one and if the HDD is part of a RAID, that file will be copied on all other drives. In theory, this is for redundancy, but in practice the damage will be worse. Once a file gets corrupted, it will be partly or entirely unreadable, therefore a text file will no longer be readable, an image file will show a random mix of colors if it opens at all and an archive shall be impossible to unpack, so you risk losing your website content. Although the most commonly used server file systems feature various checks, they quite often fail to identify some problem early enough or require a vast period of time to be able to check all the files and the hosting server will not be functional in the meantime.