The drives I used for testing are Seagate SATA-II 7200.9 - one 300GB and one 400GB. Unlike other forms of RAID, JBOD does not require matched capacities, in fact this is one advantage of using Spanning. Two unequal-sized disks can be used and the total volume space is the capacity of both drives added together. As mentioned previously however, JBOD also does not provide any additional RAID performance, and speed test results are the same as running a single drive.


HD Tune shows a flat ~35MB/s transfer speed, which is very typical for a USB-connected hard drive. That equates to 280Mb/s and the theoretical bandwidth limit of USB 2.0 is 480Mb/s, so we're getting a little more than half of that throughput.


HD Tach displays similar results, with an average read ~36MB/s or around 290Mb/s. It bursts only up to 37.5MB/s so this is probably about the limit of what USB 2.0 can do.

Let's wrap things up with some final thoughts and conclusion.