Western Digital Corp’s strenuous efforts to get its debt down are being rewarded, and Standard & Poor’s Corp said raised the rating on the Irvine, California disk drive maker’s subordinated debt to B-minus from triple-C-plus. The implied senior rating is B-plus, and the rating reflects continued improvement in both profitability and financial flexibility, and the outlook is positive. Further modest rating improvement depends on Western Digital’s ability to sustain profitability, introduce new products successfully, and maintain balance sheet strength, the New York ratings agency concluded.