Hi @illusion_rox
You are correct. VDC is only a Nexus 7000/7700 technology.
There are so many reasons why you would want a VDC:
+ first, it is a control plan and data plane virtualization protocol, meaning each VDC will have it's own dedicated control plane and specific ports/line cards will only be used in that specific VDC. This means, you can have different layers in your network architecture composed of different VDCs. Basically it will be only one physical switch. Example below: Core, Agg1, and Agg2 are three VDCs of the same Nexus 7K, but logically the topology will look like the one from the left.
![vdcss.png vdcss.png](https://community.cisco.com/t5/image/serverpage/image-id/75427i88CDD2214D842464/image-size/large?v=v2&px=999)
+ there are special features which needs a dedicated VDC: OTV and Storage VDC.
I would encourage to read the VDC whitepaper: https://www.cisco.com/c/en/us/products/collateral/switches/nexus-7000-series-switches/white_paper_c11-701112.html
You will find more examples and use cases.
Stay safe,
Sergiu