Once a file is gone, it’s gone, right? Well, it all depends. In many cases files are not physically removed from hard disks, but simply hidden from users by the operating system, and left available to be overwritten by new files. That means that some degree of disaster recovery may still be possible if a file has not been totally erased. It also means that data that needs to be permanently destroyed needs more than a simple ‘delete’. The flip side is also true: files you thought you’d saved may be unrecoverable in a crisis if your networking or backup policies are not appropriately adapted.
Whitepapers on file deletion give details on common misunderstandings about disaster recovery on deleted files. They include the way that the Microsoft Recycle Bin only retains files deleted within Windows Explorer, and the intricacies of recovering files from file shares on network file servers. Other sources provide insight into deliberate data destruction, discussing the possibility or not of a third party recovering data you thought you had permanently removed. For today’s disk drives, systematically overwriting every sector with the same character is enough to literally erase any previous data recorded.
Other information includes what it takes to destroy a hard disk, either deliberately or unintentionally. The platters, meaning the recording surfaces where the data is stored, are the only parts of a hard drive that are essential for disaster recovery of data. They are generally well-protected from hazards such as fire. In many cases, whether or not files are deleted is likely to be determined by whether or not the disk drive is in operation when a potentially destructive event occurs. If the drive heads are reading or writing to a platter, then a scratch along its length may mean that files are lost forever.