Use separate IP subnet for purpose of storage server for securiy ?

Hi folks.

I do have an old 32 bit workstation, but is running Linux just well (Elive 32 bit distro).

I intend to put some old harddrives in it and use it as a storage server. This is what I want for it:

• Not be able to connect to internet by using a different IP subnet (hopefully this work)
• I also want it to be unacessible from all devices connected to the router - exept the workstation (there aare multimedia files that I want to use the 32bit computer to have backup)
• The server should have two IP's - one fixed (to ssh from the workstation) and the other IP being dynamic.
• The dynamic IP on the 32bit server should be possible to deactivate and activte by command, while the fixed IP should always be "on". That is because I want to activate the dynamic IP only for the purpose of getting software updates.

I want to have a discussion on this. I may be completely wrong here, does this concept give any sense in a household?
Does the concept make any better safety - if I somehow get a friend for a visit, he use my wifi for internet access and happens to have some malware that infect/encrypt every possible device it finds then I want to be sure it cannot access that backup server.

Thanks in advance
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