Snooping inside some WD metadata files I saw that even the internal disk is seen as a USB device. Today copying files from my computer to a USB disk 2.5" I noted that the transfer rate is practically the same as obtained by copying the data on the WD Live TV Hub via a network. Speed may be limited simply by internal connection of the USB disk?
The bottleneck is not the internal HDD in the hub.
The internal hard drive in the WD hub is a SATA drive. All of WD 1TB sata drives designed for quiet low power audio/video applications can transfer data at 3Gbps, or about 300 megabytes/second in ideal situations. (I am just assuming that WD put a WD disk drive in the WD TV live hub and not a Seagate, for example.) The sata interface in the hub could be 1.5Gb/s and not 3Gb/s but that still works out to 150MB/s.
USB-2 spec is 480Mbps or about 48MB/s, but in practice you’ll get a little less - say about 40 Megabytes/sec.
Standard 100Mbps ethernet will give you close to 10 Megabytes/sec.
Gigabit ethernet can go much faster in theory, but in practice you will not get the full 100MB/s speed. If you are fully gigabit ethernet it works out to somewhat faster than USB-2 speeds.
Bottom line: The HDD in the WD hub transfers data to/from the hub’s processor faster than the hub’s processor can move the data over USB cable, USB/Wifi or Ethernet. As long as the HDD is faster in the moving-data department than the external interfaces it really doesn’t matter much how fast it is. It could be the slowest, lowest power drive available (likely) or the worlds fastest seeking and spinning 10000 RPM drive (unlikely) and you wouldn’t notice.
The drive in the hub is a WD Scorpio Blue (SATA 3 Gb/s)