In a magnetic or optical disk drive the integrity of data written on a disk is verified by writing data to a portion of the disk, and immediately reading the data from the disk after it has been written. If there is error in reading the data and/or the data read from the disk is substantially different from the data written to the disk an error condition is generated. The error condition may be reporting the error to the host which decides whether to rewrite the data or immediately rewriting the data without further instructions from the host.
A system for detecting thermal asperities and magnetic defects on a disc. The system includes a wide write head and a certification head. The wide write head includes a thermal asperity detector and a write element. A method for detecting thermal asperities and magnetic defects comprising writing a track with the wide write head, reading defects with the certification head, and scanning for thermal asperities with the thermal asperity detector. A burst pattern can be written to the disc upon locating a asperity of defect.
In a perpendicular magnetic recording system, the data that is being written by the write channel is fed back into the read channel. The read channel processes the data and decides if the written sequence is likely to have very poor DC characteristics. If that is the case, the write channel changes a scrambler seed and rewrites the data using the new scrambler seed. The data may also be inspected for patterns that might cause large baseline wander before being written to disk, i.e., in the write channel. A data sequence may be repeatedly scrambled and encoded until an acceptable level of estimated DC-wander has been achieved. The data sequence may then be written to disk.
In a perpendicular magnetic recording system, the data that is being written by the write channel is fed back into the read channel. The read channel processes the data and decides if the written sequence is likely to have very poor DC characteristics. If that is the case, the write channel changes a scrambler seed and rewrites the data using the new scrambler seed. The data may also be inspected for patterns that might cause large baseline wander before being written to disk, i.e., in the write channel. A data sequence may be repeatedly scrambled and encoded until an acceptable level of estimated DC-wander has been achieved. The data sequence may then be written to disk.
