Agreed,
... and if you are insistent on determining speeds, you may want to measure it in Mbps. A couple of quick search will yield a maximum USB 2.0 speed of 480Mbps; a Gigabit NIC provides twice that.
To get a better sense of what you can actually achieve in your environment, you'll need the throughput specs for:
- Your systemboard USB 2 bus
- Enclosure USB 2 bus
- Throughput of the HDD to the Enclosure bus
From a network perspective, you'll need the throughput specs for:
- Your network switch
- Your systemboard NIC speed
- DNS-323 NIC speed
- Throughput of the HDD in the DNS to the backplane
HTH,