DIG: Rapid Characterization of Modern Hard Disk Drive and Its Performance Implication

In this work, we develop novel disk characterization suite, DIG (disk geometry analyzer), which allows us to rapidly extract and to characterize the key performance metric of modern hard disk drive. Development of this tool is accompanied by thorough examination of four off-the-shelf hard disk drives. DIG consists of three key ingredients: O(1) track boundary detection algorithm,O (log n) zone boundary detection algorithm, and hybrid sampling based seek time profiling. We particularly focus on addressing the scalability aspect of disk characterization. With DIG, we are able to extract key metrics of hard disk drive within 3-20 min. DIG allows us to determine the sector layout mechanism of the underlying hard disk drive, e.g. hybrid serpentine, cylinder serpentine and surface serpentine, and to build complete sector map from LBN to three dimensional space of (cylinder, head, sector). Examining the disks with DIG, we found a number of important observations. Modern hard disk drive puts great emphasis on minimizing the head switch overhead. This is done via sector layout mechanism and and surface serpentine and hybrid serpentine is the typical way of avoiding it. Legacy disk seek time model leaves much to be desired to be used in modern hard disk drive especially in short seeks (less than 5000 tracks).