How do I set up network cards on a network consisting of a Windows 7 computer, an unmanaged switch, a NAS, and a router?

Question

Computer networks

Good day everyone!

I need help setting up two network cards in a network consisting of a Windows 7 computer, an unmanaged switch, a Synology NAS, and a router.

Given:

• A computer with two network cards running Windows 7;
  
• Unmanaged 8 port Cisco switch;
  
• Synology NAS with 4 network interfaces;
  
• SERCOMM router providing Internet access;
  
• The computer and NAS receive IP addresses from the router via DHCP;
  
• Addresses are in the format 192.168.XY, subnet 255.255.255.0
  

Almost a problem:
When copying data from a computer to a NAS, the network interface of both the computer and the NAS is "clogged" completely. This is normal and is not a problem. If, at the time of copying data from the computer, you start downloading something from the Internet, then performance failures appear on the NAS, because the network interface of the computer is busy processing data from the Internet.

Find:
Actually, I'm asking for help in setting up network interfaces on the computer and NAS so that it works as shown in the picture (see attachment):

• Local traffic, be it HTTP(S) or SMB, goes through one physical interface;
  
• Internet traffic goes through a different physical interface.
  

The need for this solution is dictated by the fact that both the computer and the NAS can "do business" both on the local network and on the Internet, that is, both the computer and the NAS can communicate with the Internet and at the same time exchange data with each other. To increase performance, I want to separate data exchange with different networks via different network interfaces.

Solution:
As far as I understand, we need to come up with some kind of new network and bring one interface on the computer and one interface on the NAS into it, giving them the corresponding static addresses.
The problem is to explain to both of them that local traffic must be driven through a specific interface.

Answer 1

Just set the interfaces on the NAS and PC intended for local traffic to static ip addresses from any other 192.168.xx subnet that does not match the main network for "internet". Do not set default gateways and DNS servers on these interfaces, only ip and subnet mask.
No additional movements are required.

Answer 2

I very much doubt that synology is able to occupy a 1GB channel with data from disks.
what is the basis of the belief that "the network interface of both the computer and the NAS is "full" full"? in my experience, a starter from the Internet and copying to storage systems coexist quite successfully.
in general, if there is a problem, then it is not at all in the plane in which you found it. Tell us in more detail how and how the analysis of the situation was carried out.
what you want to do is done in 5-10 minutes with smoke breaks. on another PC and storage interface, set the address from a different subnet that the router does not know about. for example 172.192.168.0/24 and connect these interfaces to the switch. all. if you want a storage system by name - register it in the host, if it doesn't matter - go to the new address. no additional routing is required.
but I suspect that this is not a solution to the problem, but its disguise - what you are doing should work without it.