1000GB Network only getting 8.2mbps read/writes from WD hub?

Everyone is talking about network speeds not being where they should be but one other factor that has not been mentioned is the Hard Drive. HD speed will also effectively limit your transfer rates. If the drive can’t write the data, then it will not allow more to be received. I did a quick Google on it but could not find out what is the speed of the hard drive in these units?