@BMWSKIER 

That does sound a it low. 

The max speed for Cat 5 is 100 so that may be part of the issue. Try Cat 5e or Cat 6.

Also check the USB cable as it may have issues. 

USB drive on a router was never meant to replace a NAS as that is not the main function of a router. 

  @BMWSKIER 

BMWSKIER wrote

I tested the file transfer speed form my computer(attached with cat-5 cable) to the modem. The speed never exceeded 54MPS! This barely exceeds the USB 1.0 specification!

Totally useless for largre file transfers.

 

My mis-quote! I'm using Cat 5e which has a 1 GBPS transfer speed.