Another problem that arises for the file system is determining the proper range for a request. How much flexibility is needed by the disk in order to perform well?
In general, the larger the range given to the disk, the more positioning time is reduced. The simulation results presented in Section 4 indicate that track-sized ranges effectively remove rotational costs while larger sized ranges (e.g., several thousand blocks) help with seek costs. In the ideal case, positioning time can be almost entirely removed if the size of the target range matches the span of the current workload.
0 Of course, one could extract low-level information from the drive, including track size, using microbenchmarks [37].
Thus, the file system should specify the largest range that best matches its allocation and layout policy. For example, FFS could specify that a write be performed to any free block within a cylinder group.