Embedded servo

Embedded servo or wedge servo is a type of servo configuration used on hard disks. 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 computers in the late 1980s.