Landing zone (hard drive)
As a landing zone ( English landing zone ) is a protection device for the switching off of a disk , respectively.
During normal operation of a hard disk drive , the rotational movement of the storage disks entrains air molecules. This creates an air flow under the read / write heads , which causes them to lift off the surface ( hydrodynamic slide bearing ). When the disk is switched off, the heads would touch the information-bearing disk surface and cause damage there, which can lead to data loss. To prevent such a head crash , there is a special cylinder that does not contain any user data and on which the read / write heads land when the disk is switched off - the landing zone.
The landing zone is now approached automatically (Autopark function, since 1989); In the past, a special parking command had to be given via the interface, which led to problems, especially in the event of unintentional shutdown and sudden voltage losses. Today, if the supply voltage fails, the motor is used as a generator and the rotational energy of the plate is used for the parking process.
With modern drives, the heads no longer land on the surface, instead the head mechanism drives on small ramps when approaching the landing zone, which ensure a safe distance between the heads and the surface, or the heads are moved out of the platters. In this way, not only the surfaces, but also the heads are protected from wear and tear. After approaching the landing zone, the head mechanism is fixed there to prevent the heads from moving when the plate is being transported. This is usually done by a small permanent magnet that holds the head mechanism in the park position.