Patent ID: 7609470

Claim:
An information storage device having a recording medium and a head to write information into the recording medium, and controlling a steady state value, an overshoot value or an overshoot width of a write current for writing into the recording medium, the device comprising: a Viterbi Metric Margin measurement section to measure a Viterbi Metric Margin; and a write current setting section to set the write current, based on a value of the Viterbi Metric Margin measured by the Viterbi Metric Margin measurement section, such that a data writing spot is prevented from spreading during writing into the medium and occurrence of side erasure is prevented; wherein the Viterbi Metric Margin measurement section further measures a value of a lead Viterbi Metric Margin at the beginning of writing into the recording medium, and the write current setting section sets the write current so as to prevent deterioration in signal quality at the beginning of writing, based on the measured value of the lead Viterbi Metric Margin.