Embedded servo
Encyclopedia
Embedded servo or wedge servo is a type of servo
configuration used on hard disk
s. Embedded servo systems embed the feedback signals for the read/write head positioner (usually a voice coil
motor) inside gaps (wedges) in the data tracks of the disk. This setup allows the entire set of platters to be used, instead of having to reserve one or two surfaces for the servo's use, which makes more space for data available on the drive. Embedded servo was originally developed in the 1970s, and started to appear on mass-market hard drives for personal computer
s in the late 1980s.
As with dedicated-servo drives, the control signals are written at the factory using a special device called a servowriter
, and cannot usually be regenerated in the field. Drives with errors in the servo areas are considered to be badly damaged and should be replaced.
Servomechanism
thumb|right|200px|Industrial servomotorThe grey/green cylinder is the [[Brush |brush-type]] [[DC motor]]. The black section at the bottom contains the [[Epicyclic gearing|planetary]] [[Reduction drive|reduction gear]], and the black object on top of the motor is the optical [[rotary encoder]] for...
configuration used on hard disk
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...
s. Embedded servo systems embed the feedback signals for the read/write head positioner (usually a voice coil
Voice coil
A voice coil is the coil of wire attached to the apex of a loudspeaker cone. It provides the motive force to the cone by the reaction of a magnetic field to the current passing through it...
motor) inside gaps (wedges) in the data tracks of the disk. This setup allows the entire set of platters to be used, instead of having to reserve one or two surfaces for the servo's use, which makes more space for data available on the drive. Embedded servo was originally developed in the 1970s, and started to appear on mass-market hard drives for personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
s in the late 1980s.
As with dedicated-servo drives, the control signals are written at the factory using a special device called a servowriter
Servowriter
A servowriter is a complex machine used in the manufacturing of a hard disk drive. It is used to write servo tracks on the disk platters which make up part of the servomechanism that positions the actuator arm....
, and cannot usually be regenerated in the field. Drives with errors in the servo areas are considered to be badly damaged and should be replaced.