Data corruption is the damage of data due to various software or hardware problems. The moment a file gets corrupted, it will no longer work properly, so an application will not start or shall give errors, a text file will be partially or entirely unreadable, an archive will be impossible to open and then unpack, etc. Silent data corruption is the process of information getting damaged without any acknowledgement by the system or an administrator, which makes it a serious problem for web hosting servers as problems are much more likely to happen on larger hard disks where vast volumes of info are located. If a drive is part of a RAID and the info on it is duplicated on other drives for redundancy, it's more than likely that the bad file will be treated as an ordinary one and it'll be copied on all of the drives, making the damage permanent. A huge number of the file systems that operate on web servers today often are not able to recognize corrupted files in real time or they need time-consuming system checks during which the server isn't working.