External Hard drives

I have the WD Live Hub - 1tb with the most recent firmware my question is: Is there a limit to the number of external drives that can be connected to this device?

I currently have 5 External drives conncected Via 1 usb hub w/ 4 connections = 12 TB and one connected to the front USB port = 1tb and i wanted to connect another hub on the front port but it dosent seem to like it very much it will detect and read the 1st drive but not any more after that.  any ideas on this anyone???

This is a matter of trial and error as this particular setup is not supported. 

Search forum for selfpowered usb hub. Some users are using those. I used to use network usb hub.