Method for adjusting linear recording density and magnetic disk drive

A method, implemented in a magnetic disk drive, for adjusting a linear recording density, the magnetic disk drive comprising one or more disks and two or more heads, the one or more disks comprising two or more recording surfaces, the two or more heads being associated with the respective two or more recording surfaces, each of two or more recording surfaces comprising a plurality of zones, the method comprising:

• obtaining a first flying-dependent error sensitivity for each of the two or more heads, the first flying-dependent error sensitivity representing a change in read error rate corresponding to a change in flying height of the head during write;
• comparing the obtained first flying-dependent error sensitivity of each of the two or more heads with a threshold;
• and
• reducing a linear recording density of a first recording surface associated with a first head of the two or more heads if a first flying-dependent error sensitivity of the first head is higher than the threshold,
• wherein obtaining the first flying-dependent error sensitivity comprises
• measuring a first read error rate and a second read error rate for each of a plurality of combinations of the two or more heads and the plurality of zones, the first read error rate and the second read error rate each being indicative of a rate at which a read error occurs when data is written to the zone of the recording surface associated with the head and then the written data is read, in a first state and a second state, respectively, in which the head has different flying heights;
• and
• obtaining a second flying-dependent error sensitivity for each of the plurality of the combinations based on the first read error rate and the second read error rate, the second flying-dependent error sensitivity representing a change in the read error rate corresponding to a change in the flying height of the head during write;
• and
• obtaining, for each of the two or more heads, an average value of the obtained second flying-dependent error sensitivities for the combinations of the head and the respective plurality of zones as the first flying-dependent error sensitivity.

A magnetic disk drive comprising:

• one or more disks each comprising two or more recording surfaces;
• two or more heads associated with the respective two or more recording surfaces, each of two or more recording surfaces comprising a plurality of zones;
• a flying-dependent error sensitivity obtaining controller configured to obtain a flying-dependent error sensitivity for each of a plurality of combinations of the two or more heads and the plurality of zones, the flying-dependent error sensitivity representing a change in read error rate corresponding to a change in flying height of the head during write;
• a determination controller configured to determine whether the obtained flying-dependent error sensitivity of each of the plurality of combinations is higher than a threshold by comparing the obtained flying-dependent error sensitivity with the threshold;
• a linear recording density adjuster configured to reduce a linear recording density of a first zone of a first combination if a flying-dependent error sensitivity of the first combination is higher than the threshold;
• and
• a calculator configured to calculate a capacity of the magnetic disk drive in a state in which the linear recording density is reduced,
• wherein the linear recording density adjuster is further configured to:
• identify a second combination having a lowest flying-dependent error sensitivity, among the obtained flying-dependent error sensitivities of the plurality of combinations, if the calculated capacity is smaller than a target capacity;
• and
• increase a linear recording density of a second zone of the identified second combination.