How to async-mirror 2 air-gapped GitLab EE servers?

Does self-hosted, GitLab EE provide the ability to asynchronously-mirror two air-gapped GitLab EE servers, each server with the same host/domain name? We would transfer data between the 2, air-gapped networks periodically (at most twice a day to start; more likely a couple times a week) via a simple, physical storage device (like an external SSD connected via USB).

Our team would provide the means to synchronize the DNS in the 2 separate, air-gapped networks that “house” the GitLab servers.

A related question: is there a document that described what data is created/stored outside of the git-repo content? Git can nicely handle asynchronous, decentralized updates. Maybe we (our team) could follow special procedures to manage, encapsulate, and sync the not-git-repo data - if we new the scope of what that data might be.

For example: can GitLabEE Issues be stored in a git repo, or in something else?