A magnetic disk device includes a disk, first and second heads, a motor, and a controller. The disk includes a first surface and a second surface opposite to the first surface. The first head is configured to perform reading and writing with respect to the first surface. The second head is configured to perform reading and writing with respect to the second surface. The motor is configured to move the first and second heads with respect to the first and second surfaces, respectively, along a radial direction of the disk. The controller is configured to alternately activate the first and second heads to perform writing of a plurality of spiral patterns on the first and second surfaces of the disk, respectively, while controlling the motor to move the first and second heads at a predetermined constant speed with respect to the first and second surfaces in the radial direction.

Systems and methods are disclosed for phase locking of a clock. In some embodiments, a phase locked clock (PLC) module can phase-lock a write clock to a media written with multiple servo zones of different frequencies. In some implementations, this can be utilized to perform a self-servo write (SSW) of a disc surface within a hard disc drive (HDD). A PLC module can perform a method of writing with a single frequency phase coherently while a read element passes over servo zones with different frequencies. While the PLC module can perform such methods for a SSW process, the methods can also be utilized for other applications that can benefit from writing with a single frequency phase coherently based on servo zones with different frequencies.

According to one embodiment, a magnetic disk device comprises a disk, a head that writes data to the disk and reads data from the disk, and a controller that controls a position of the head so as to write a first spiral servo pattern to the disk, and overwrite a second spiral servo pattern different from the first spiral servo pattern by shifting in a radial direction of the disk from the first spiral servo pattern.

A method for positioning a magnetic head having first and second read sensors and one write head includes: while the magnetic head is at a first position relative to a disk medium, reading first magnetic servo information written on a first surface of the disk medium, with the first read sensor, and reading second magnetic servo information written on the first surface of the disk medium with the second read sensor; determining a position error of the magnetic head based on the first and second magnetic servo information; and repositioning the magnetic head to a second position relative to the disk medium to compensate for the determined position error of the magnetic head.

Storage device self-servo-write includes generating a time base frequency signal, generating a sampled frequency signal by sampling the time base frequency signal at a sample rate to obtain a first set of samples, decimating those samples at a decimation rate to obtain a second set of samples at a spiral frequency of which the time base frequency is a first integer multiple, detecting a spiral track based on the spiral frequency, and writing a servo pattern based on the spiral track and the time base frequency. A generated sampled frequency obtained by sampling the time base frequency signal at the sample rate is used as the servo write frequency, of which the time base frequency is a second integer multiple. Alternatively, the time base frequency is multiplied by a first rational multiple so that the time base frequency is a second rational multiple of the servo write frequency.

According one embodiment, a servo write method includes a head and a disk having a plurality of spiral servo patterns which are written radially in a first direction from a first area to a second area other than the first area at velocity that varies between the first area and the second area, the method including moving the head in a second direction opposite to the first direction to read each of the spiral servo patterns, measuring a plurality of time intervals at which each of the spiral servo patterns is read in the first area, and writing a plurality of servo patterns to the first area based on the time intervals.

According to one embodiment, a servo write method includes a head and a disk having a plurality of spiral servo patterns which are written radially in a first direction from a first area to a second area other than the first area at velocity that varies between the first area and the second area, the method including moving the head in a second direction opposite to the first direction to read each of the spiral servo patterns, measuring a plurality of time intervals at which each of the spiral servo patterns is read in the first area, and writing a plurality of servo patterns to the first area based on the time intervals.

According to one embodiment, a magnetic disk device comprises a disk, a head that writes data to the disk and reads data from the disk, and a controller that controls a position of the head so as to write a first spiral servo pattern to the disk, and overwrite a second spiral servo pattern different from the first spiral servo pattern by shifting in a radial direction of the disk from the first spiral servo pattern.

Zone self-servo write (SSW) technology is disclosed that leverages two clock signals synchronized in parallel to transition between zones to write servo patterns at different frequencies while minimizing error rate despite the different frequencies. Two separate clock signals (clocks) are used to locate and lock to different reference spirals. By updating both clocks in parallel instead of in series, error rate for writing while stepping up frequency across zones is reduced.

Systems and methods for servo zone transition optimization are described. In one embodiment, the storage system device includes a disk drive and a controller. In some embodiments, the controller may be configured to assess at least one operation of a read/write head of the disk drive; and format, based at least in part on the assessing of the read/write head, a disk surface of the disk drive with a first servo zone, a second servo zone, and an overlap region extending between a start point of the second servo zone and an end point of the first servo zone. In some cases, the overlap region starts towards a disk inner diameter (ID) and ends towards a disk outer diameter (OD).