Data corruption is the unintentional change of a file or the loss of info which often occurs during reading or writing. The reason can be hardware or software failure, and as a result, a file could become partially or completely corrupted, so it'll no longer work properly since its bits will be scrambled or missing. An image file, for instance, will no longer show a real image, but a random mix of colors, an archive will be impossible to unpack because its content will be unreadable, etcetera. When such an issue appears and it is not noticed by the system or by an admin, the data will get corrupted silently and if this happens on a drive which is part of a RAID array where the info is synchronized between various drives, the corrupted file will be copied on all other drives and the harm will be permanent. A large number of popular file systems either do not offer real-time checks or don't have high quality ones which will detect an issue before the damage is done, so silent data corruption is a rather common problem on hosting servers where substantial volumes of information are stored.