Hard disk drive failure

A hard disk drive failure occurs when a hard disk drive malfunctions and the stored information cannot be accessed with a properly configured computer. A hard disk failure may occur in the course of normal operation, or due to an external factor such as exposure to fire or water or high magnetic fields, or suffering a sharp impact or environmental contamination, which can lead to a head crash. The stored information on a hard drive may also be rendered inaccessible as a result of data corruption, disruption or destruction of the hard drive's master boot record, or by malware deliberately destroying the disk's contents. There are a number of causes for hard drives to fail including: human error, hardware failure, firmware corruption, media damage, heat, water damage, power issues and mishaps. Drive manufacturers typically specify a mean time between failures (MTBF) or an annualized failure rate (AFR) which are population statistics that can't predict the behavior of an individual unit. These are calculated by constantly running samples of the drive for a short period of time, analyzing the resultant wear and tear upon the physical components of the drive, and extrapolating to provide a reasonable estimate of its lifespan. Hard disk drive failures tend to follow the concept of the bathtub curve. Drives typically fail within a short time if there is a defect present from manufacturing. If a drive proves reliable for a period of a few months after installation, the drive has a significantly greater chance of remaining reliable. Therefore, even if a drive is subjected to several years of heavy daily use, it may not show any notable signs of wear unless closely inspected. On the other hand, a drive can fail at any time in many different situations. The most notorious cause of drive failure is a head crash, where the internal read-and-write head of the device, usually just hovering above the surface, touches a platter, or scratches the magnetic data-storage surface.