According to one embodiment, a magnetic disk device includes a disk including a first track including a first sector, a second sector, and a first parity sector, a head, and a controller configured to, when writing a second track adjacent to the first track in the first direction, even if, in a third sector of the second track adjacent to the first sector in the first direction, a first upper limit in a second direction opposite to the first direction, continue the processing of writing data to the third sector, and if, in a fourth sector adjacent to the second sector in the first direction, a second upper limit in the second direction, stop the processing of writing data to the fourth sector.

A data storage device is disclosed comprising a head actuated over a disk. A first plurality of codewords and corresponding parity sector are generated, and a second plurality of codewords and corresponding parity sector are generated. The first and second plurality of codewords are written to the disk, and during a read of the first and second set of codewords, M codeword locations within the data track that are unrecoverable are saved, and N codeword locations out of the M codeword locations are selected based on a quality metric of the read. The N codewords are reread from the data track at the N codeword locations and reliability metrics associated with the N codewords are saved. The saved reliability metrics are updated using at least one of the first parity sector or the second parity sector.

A tape drive system for ensuring tape data integrity by tape surface inspection, the tape drive system being configured for reading and writing data from/to a magnetic tape, is provided. The tape drive system includes a laser inspection unit comprising a sender and a receiver integrated into the tape drive system, wherein the laser inspection unit configured for recognizing a tape defect by scanning the magnetic tape when the tape drive system is in operation. The tape drive system includes a read/write head configured for acting together with the laser inspection unit as sensors for providing sensor data during a read/write operation of the tape drive system, a communication link between the sensors and a controller unit for exchanging sensor data. The controller is configured for evaluating sensor data and for triggering predefined actions based on the respective evaluation results such that the tape data integrity is ensured.

A method includes determining whether a tunneling magnetoresistance (TMR) sensor is corroded using resistance, amplitude and signal to noise ratio (SNR) measurements of the sensor. A method to determine whether a TMR sensor is corroded includes determining an expected initial resistance value, R.sub.TMRoUse and measuring a resistance value, R.sub.TMR, of the sensor. The method includes calculating a ratio of the R.sub.TMR value and the expected initial resistance value, R.sub.TMRoUse and determining whether the ratio is in a predefined range for the TMR sensor. In response to determining that the ratio of the sensor is within the predefined range, the method includes outputting an indication that the TMR sensor is corroded. In response to determining that the ratio of the sensor is outside the predefined range, the method includes outputting an indication that the TMR sensor is not corroded.

A magnetic disk device includes a magnetic disk, a read head for reading data from sectors and tracks of the magnetic disk, a read channel including a first circuit configured to process an output signal from the read head according to a value of a parameter, and processor. The processor is configured to, upon detection of a read error while the read head is reading data from an error sector of an error track, determine an error amount in each sector in the error track, select from the error track a plurality of sectors having an error amount that is within a predetermined range from an error amount of the error sector, perform a training read on the selected sectors, determine a new value of the parameter based on the training read, and set the new value of the parameter for the read channel.

A data storage device is disclosed comprising a head actuated over a disk comprising servo data for defining a plurality of data tracks, wherein each data track comprises a plurality of data segments. First data is written to data segments of a first data track, and second data is written to data segments of a second data track. After writing the second data, the first data is read at multiple off-track offsets of the first data track to measure an average off-track read capability (OTRC) of the first data track. A cross-track profile is generated for a first data segment of the first data track, and at least part of the cross-track profile is correlated with the measured average OTRC.

Systems and methods are disclosed for reducing adjacent track erasure from write retry operations. In certain embodiments, an apparatus may comprise a circuit configured to abort a write operation while writing to a selected sector of a disc storage medium during a first revolution of the disc storage medium, and mark the selected sector as a temporary bad sector in a mapping table. The circuit may perform a write retry to continue the write operation starting at a next sector contiguously following the selected sector, without attempting to write the selected sector again, during a second revolution of the magnetic disc.

According to one embodiment, a magnetic disk device includes a magnetic disk, a first magnetic head and a second magnetic head that are moved independently of each other, a first controller chip, a second controller chip, and a third memory. The first controller chip includes a first processor and a first memory, and controls the first magnetic head. The second controller chip includes a second processor and a second memory, and controls the second magnetic head. Management information is stored in the third memory. The first controller chip is connected to the third memory. The second controller chip is connected to the third memory via the first controller chip. The second controller chip saves the management information into the second memory.

In a storage system that implements RAID (D+P) protection groups a drive subset initially has (D+P) drives plus a spare drive with (D+P) splits. Spare splits are distributed with drive index and split index adjacency such that no single drive or split index contains multiple spare splits. When the drive subset is incremented by one drive a group of selected splits are relocated to the new drive based on drive index and split index adjacency such that no single drive or split index contains multiple members of a new protection group. If one of the drives is failing or fails, then an adjusted spare split index value is calculated for each protection group member on that drive so that the protection group members are rebuilt or relocated without placing more than one member of any protection group on a single drive. Adjusted spare split index values may be calculated in steps using the data split indices in ascending order and the largest drive indices in descending order.

According to one embodiment, a magnetic disk device includes a magnetic disk, a first magnetic head and a second magnetic head that are moved independently of each other, a first controller chip, a second controller chip, and a third memory. The first controller chip includes a first processor and a first memory, and controls the first magnetic head. The second controller chip includes a second processor and a second memory, and controls the second magnetic head. Management information is stored in the third memory. The first controller chip is connected to the third memory. The second controller chip is connected to the third memory via the first controller chip. The second controller chip saves the management information into the second memory.