Analysis: The Impact Of Shifting From 512 Byte To 4 KB Sectors

512 Byte Sectors: Toshiba MK6465GSX (640 GB)

This 2.5” 640 GB drive is probably the last one in Toshiba’s portfolio to employ conventional 512 byte sectors. It spins at 5400 RPM and has 8 MB cache memory as well as a SATA 3 Gb/s interface. The drive is available at 160, 250, 320, 500, and 640 GB capacities, but we used the 640 GB flagship for this comparison with its successor.

We found that this older model has a higher interface bandwidth of 204 MB/s (as opposed to 183 MB/s on the newer 750 GB drive with 4 KB sector size). However, effective throughput is higher on the newer drive by quite a significant amount. The latter is a result of improvements in data density, as well as the modified sector size.

In terms of I/O performance, we found that the MK6465GSX is slightly ahead of the 750 GB MK7559GSXP, but the difference is hardly relevant. The only time when the older drive is significantly faster is when it is compared to the newer 4 KB sector size drive that runs at misaligned logical 512 byte sectors. See the benchmark section for details.