The primary development focus for spinning disks over the last several years has been on increasing the capacity of a single disk. Data transfer rates have improved only slightly. In fact, simply due to the laws of physics larger spinning disks show a greater variability for data transfer rates between data stored on the outer slices versus the inner slices of the disk. Therefore, to achieve good consistent performance you should choose smaller rather than bigger disks. For example, choose 146 GB disks over 500 GB (or larger) disks.

Faster spinning disks at 15k RPM have higher throughput rates than slower 10k RPM or 7.2k RPM disks. In an ideal case a single spinning 15k RPM disk can sustain up to 150 MB/s data transfer.