How to create a working forum mirror?

Question

Search Engine Optimization

Good afternoon!
The task is to create a working forum mirror on a new domain, on a new hosting and in the com zone.
The working mirror must be synchronized with the main forum site and vice versa. That is, when new records appear on both sites, they must be synchronized. Is it possible? If so, in what direction should one think?
Subsequently, the mirror is planned to be made the main one? Will your main site traffic drop? Or will it straighten out?

Answer 1

Before moving, the mirror must be closed from indexing by writing the following 2 lines in robots.txt:

User-agent: *
Disallow: /

When re-gluing, put a 301 redirect and duplicate the contents of the robots.txt of the main site. Traffic can sag, but not more than 20%, usually restored within six months.