| Questions & Answers About Hard Disk Drives (HDD) & Recovering Data
Q: What is a "hard drive" or a "hard disk drive"?
A: The term "Hard Drive" (HD) or "Hard Disk Drive" (HDD) refers to the primary data storage device within a computer system. It contains one or more aluminum (or glass) disks that are coated with a magnetic coating. The disks spin at speeds up to 15,000 rotations per minute (RPM), and the read / write heads move across the disk surfaces to transfer data to and from the disks.
Q: Do disk drive heads actually touch the disk surface?
A: No - the read / write heads within the hard drive literally "fly" on a cushion of air (or an "air bearing") that is created by the spinning motion of the disks. The distance between a head and the spinning disk is extremely small (less than 1/100th the width of a human hair).
Q: What is meant by the term "MTBF"?
A: It stands for "Mean Time Between Failure". It represents the manufacturers' estimate of how long a particular hard drive will last before it stops working. This estimate may be expressed as a number of hours, or as the number of start and stop cycles the drive will endure before it fails. Many times the MTBF number exceeds the practical useful life of the storage device. A disk drive with a manufacturers' MTBF of 300,000 hours (or 34 years of continuous use) will likely be replaced long before the 300,000 hours are reached.
Q: My hard drive suddenly started making noises - is there a chance of recovery?
A: Yes. The hard drive can be making noises for any number of reasons. A "thumping" or "clicking" noise is usually caused by the inability of the heads to locate and read the first track on one or more disks. A scraping noise may indicate physical damage to the disk surface. A thorough analysis of the device will determine the extent of the damage and whether or not data can be salvaged.
Q: Can data be recovered from a re-formatted hard drive?
A: Yes - although the quantity of usable data recovered will depend on several factors, including: the operating system involved, the level of file fragmentation (if any), and the extent to which any overwrite may have occurred (as with software re-installation).
Q: I deleted files in Windows and emptied the trash - are the files still retrievable?
A: Yes. The files should still physically reside on the drive and should be recoverable. However, Windows views the area that the files occupied as "free and available" space, and may attempt to write new data files to these locations if the computer continues to be used.
Q: Can I use recovery software first to try to recover my data?
A: The safest approach to data recovery is to capture every physical block from the original storage device. The resulting "image" can then be used to recover file / folder structures and determine overall data integrity. Data recovery software programs are usually used to address the original media directly, and as such can place data at risk - especially if the drive is making noises or in a failing state. In some situations, repeated efforts to access data areas with utilities can make problems worse, or can render data unrecoverable. If the data is important, it may be better to consult with a data recovery professional before any recovery attempts are made with utilities.