A method for writing repeatable run-out data, representing a recurring contribution to position error, to a rotating constant-density magnetic storage medium, includes repeating, for each respective track at a respective radius of the constant-density magnetic storage medium, (1) determining a respective track pattern frequency based on track location and desired data density, (2) locating a position in a respective servo wedge on the respective track based on servo sync mark detection, (3) writing the repeatable run-out data to the respective servo wedge at a time delay, from the location of the position in the respective servo wedge, that is inversely proportional to the respective radius, to achieve a predetermined offset, and (4) repeating the determining, the locating and the writing for each servo wedge on the respective track of the constant-density magnetic storage medium.

A data storage device configured to access a magnetic tape is disclosed comprising a plurality of data tracks. A first head is configured to access a first data track comprising a first sync mark, and a second head is configured to access a second data track comprising a second sync mark. The first head is used to read first data from the first data track, wherein the first data comprises a plurality of symbols, and the second head is used to read the second sync mark from the second data track. The first data is symbol synchronized based on the second head reading the second sync mark from the second data track.

The present disclosure describes aspects of constant-density writing for magnetic storage media. In some aspects, a constant-density writer delays transitions between bits within write data to enable constant-density writing. The write data has an initial bit period based on a constant clock signal, which is generated based on the rotation of a media disk. The constant-density writer modifies the write data to generate phase-delayed write data, which has a bit period that is greater than or equal to the initial bit period. To realize this bit period, the constant-density writer changes write phases of bit transitions within the write data. The constant-density writer can also insert stretch bits, filter single-bit transitions, and mitigate glitches within the phase-delayed write data.

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.

According to one embodiment, a magnetic disk device includes a magnetic disk including at least one servo zone that includes a first data storage track with a first servo pattern having a first frequency and a second data storage track with a second servo pattern having a second frequency, wherein the first data storage track is located closer to an outer diameter of the magnetic disk than the first data storage track and the first frequency is greater than the second frequency; a magnetic head that faces the magnetic disk; and a zone servo switching unit that switches a servo pattern frequency employed to position the magnetic head in a radial direction based on a radial position of the magnetic head.

The present disclosure describes aspects of constant-density writing for magnetic storage media. In some aspects, a constant-density writer delays transitions between bits within write data to enable constant-density writing. The write data has an initial bit period based on a constant clock signal, which is generated based on the rotation of a media disk. The constant-density writer modifies the write data to generate phase-delayed write data, which has a bit period that is greater than or equal to the initial bit period. To realize this bit period, the constant-density writer changes write phases of bit transitions within the write data. The constant-density writer can also insert stretch bits, filter single-bit transitions, and mitigate glitches within the phase-delayed write data.

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.

A data storage device is disclosed wherein a first plurality of codewords are generated each comprising a plurality of symbols, and a first parity sector is generated over the first plurality of codewords. A second plurality of codewords are generated each comprising a plurality of symbols, and a second parity sector is generated over the second plurality of codewords. A third parity sector is generated over a first subset of the first plurality of codewords and a first subset of the second plurality of codewords, and a fourth parity sector is generated over a second subset of the first plurality of codewords and a second subset of the second plurality of codewords. When processing of a first codeword fails, the first codeword and the first parity sector are processed using a LDPC type decoder, and the first codeword and the third parity sector are processed using the LDPC type decoder.

A data storage device is disclosed comprising a storage medium. Input data is encoded according to at least one channel code constraint to generate first data and second data. The first data is encoded into a first codeword, and the second data is encoded into a second codeword, wherein a first code rate of the first codeword is less than a second code rate of the second codeword. The first codeword and the second codeword are interleaved to generate an interleaved codeword, and the interleaved codeword is written to the storage medium.

A data storage device is disclosed comprising a storage medium. First data is encoded into a first codeword comprising a plurality of i-bit symbols, and second data is encoded into a second codeword comprising a plurality of j-bit symbols, wherein i is different than j and a first code rate of the first codeword is less than a second code rate of the second codeword. The first codeword and the second codeword are symbol interleaved to generate an interleaved codeword, and the interleaved codeword is written to the storage medium.