Abstract: A method includes detecting a read error during a first read operation by a read sensor on a first track on a data storage medium. The method also includes, after the read error is detected, performing a second read operation by the read sensor on the first track, carrying out bit error value (BEV) measurements for the second read operation, and determining, from the BEV measurements, whether the read sensor produces a marginal BEV, which is between first and second predetermined BEV thresholds. In response to determining that the read sensor produces the marginal BEV, a third read operation by the read sensor on the first track is carried out, and BEV measurements for the third read operation are performed. When the BEV measurements from the second and third read operations meet at least one predetermined read sensor instability criterion, it is concluded that the read sensor is unstable.

Abstract: Various embodiments provide a recording medium. The recording medium may include a dedicated servo layer for providing servo information. The dedicated servo layer may include a plurality of tracks. A first track may include a first servo signal. A second track may include a second servo signal. The first servo signal and the second servo signal may include a plurality of common transitions. The transitions may be provided at a pre-determined frequency.

Abstract: In various embodiments, a recording medium having a servo layer configured to provide servo information and a data recording layer configured to record data, wherein the medium comprises a plurality of servo patterns and a plurality of data segment in one sector, each data segment corresponding to each of the plurality of servo patterns, wherein the plurality of servo patterns comprises a first servo pattern comprising an automatic gain control, a second servo pattern comprising a sector address mark, a third servo pattern comprising a GrayCode, and a fourth servo pattern comprising a plurality of servo bursts, wherein the data recording layer is configured to record the data on the data segments corresponding to the first, second, third and fourth servo patterns.