Disk drive reliability case study: Dependence upon head fly-height and quantity of heads

Disk drive failure data is analyzed to gain insight regarding two significant concerns. The first is whether drive reliability is highly dependent on the number of read/write heads in a disk drive. Analyses separate drives by family so that the number of heads in the drive is the single uncontrolled variable. Drives are found to have multiple failure mechanisms vying for dominance in the early life. These analyses indicate a clear dependence between reliability and the number of read/write heads. For one family there is a very strong dependence, but for the second family it is much weaker. The second concern is whether the advances in design technology and manufacturing processes are progressing fast enough to counteract the potential reliability problems associated with consistently lowered head fly-height. The analysis shows that the positive impact of technology on drive reliability is far greater than any negative effect of a lower fly-height. That is, even though the more recent drives have lower fly-heights, they are more reliable.