Nodes and downloading-storing Blockchain

Hello.

I don't suppose if anyone can tell me, can I run multiple nodes on 1 pc and do I just need to download the Blockchain once , or will I need to have multiple instances of the Blockchain i.e if I run 2 nodes I will need to hold the data twice in storage (from 800GB to 1.6TB) ? Or can they just share the same Blockchain data file ?