Data storage device formatting a disk surface with a write format and a read format

A data storage device comprising:

• a disk surface comprising a plurality of data tracks;
• a head actuated over the disk surface;
• and
• control circuitry configured to:
• define a plurality of realms on the disk surface including a first realm;
• map a first plurality of logical block addresses (LBAs) to physical block addresses (PBAs) of each realm;
• write first data to the first realm based on a first format;
• reformat at least part of the disk surface based on a second format, wherein the second format defines a lower recording density for the disk surface as compared to a recording density defined by the first format;
• and
• after reformatting the at least part of the disk surface, activate a new realm for the at least part of the disk surface that at least partially overlaps the first realm wherein a second plurality of LBAs are mapped to PBAs of the new realm.

A method of operating a data storage device, the method comprising:

• writing first data to a first part of a disk surface based on a first format;
• reformatting the first part of the disk surface based on a second format, wherein the second format defines a lower recording density for the disk surface as compared to a recording density defined by the first format;
• after reformatting the first part of the disk surface, reading the first data from the first disk surface based on the first format;
• and
• after reading the first data from the first disk surface, overwriting the first data with second data based on the second format.