Zyxell Keenetic II and external WD MyPassport, brake performance? Why?

Question

Electronics

I got it here the other day, this miracle - WD My Passport Ultra for as much as 1 GB of all kinds of information. At home, I decided to connect to Keenetic II as a network drive, or just as a visible folder through the network environment. The router instantly found and installed this hard drive in itself. The system easily connected it as a "network". But the trouble is, it really takes a very long time to rummage around. From folder to folder for a few minutes.
What is the real problem? The processor in the router is loaded by about 20% no more. The drawers are new. Could it be a power issue?