Information on saving / loading from save

Could we get some information on how / what variables are stored on save, and how saved variables are handled when a mod updates for a dedicated server?
I’d like to store an array of structures which needs to persist through saves and persist through mod updates, but I’m worried it might be wiped when updating.

Don’t touch the variable(s) in question and there shouldn’t be an issue.

That’s my understanding of it so far, anyway, but I’m no expert.