We now wish to evaluate the utility of range writes in disk schedulers. To do so, we utilize a detailed simulation environment built within the DiskSim framework [5].
We made numerous small changes throughout DiskSim to provide support for range writes. We implemented a small change to the interface so pass range descriptors to the disk, and more extensive changes to the SPTF scheduler to implement both EC and HR scheduling. Overall, we changed or added roughly one thousand lines of code to the simulator. Unless explicitly investigating EC scheduling, we use the HR scheduler.
For all simulated experiments, we use the HP C2247A disk, which has a rotational speed of 5400 RPM, and a relatively small track size (roughly 60-100 blocks, depending on the zone). It is an older model, and thus, as compared to modern disks, its absolute positioning costs are high whereas track size and data transfer rates are low. However, when writing to a localized portion of disk, the relative balance between seek and rotation is reasonable; thus we believe our results on reductions in positioning time should generalize to modern disks.