The software we use for measuring hard disk drive performance, DiskSpeed32, performs really long tests, since it reads all sectors on the hard disk measuring the achieved transfer rate and plotting a graph.
Normally the hard disk transfer rate varies according to the part of the disk that is being read. The disk transfer rate is higher at the disk’s edge, lowering as it approaches its center. This occurs because of the zone bit recording (ZBR): in longer tracks (the ones away from the disk center) there are more sectors and more data is read at each disk spin. Because of that, the software used shows three results: maximum transfer rate (obtained on the first disk cylinders, i.e., on the tracks located near the disk edge), minimum transfer rate (obtained on the last disk cylinders, i.e., on the most inner tracks), and average transfer rate, which is the result that we are usually interested in knowing.
Because of this effect we can also explain the need of hard disk defragging and why professional disk defrag utilities such as Norton Speed Disk allow you to move the operating system files to the beginning of the hard disk. As we explained, data stored on the beginning of the disk are read at a higher transfer rate than data stored in other sectors.
We used a Seagate Barracuda 7200.10 160 GB (ST3160815AS, SATA-300, 7,200 rpm, 8 MB buffer) hard disk drive to perform our tests. First we installed it directly on an empty SATA-300 port on our motherboard to see what the performance of this drive is while it is installed inside the PC. We also installed our hard drive on another HDD enclosure (Thermaltake Max 4) to compare the results. This other enclosure also has an eSATA port so we are also including the results achieved using this connection for you to have an idea of the performance difference between eSATA and USB 2.0.
Thermaltake BlacX achieved exactly the same performance as Thermaltake Max 4 using USB 2.0 connection. The big problem with USB 2.0 is the low performance compared to the SATA port: our hard disk drive installed on the SATA port achieved a maximum transfer rate 237% higher and an average transfer rate 145% higher. As you also can see on our chart eSATA port makes the hard disk drive to achieve the same performance as if it were installed inside the PC. BlacX, however, doesn’t have this connectivity option.