I have a 56 TB local Unraid NAS that is parity protected against single drive failure, and while I think a single drive failing and being parity recovered covers data loss 95% of the time, I’m always concerned about two drives failing or a site-/system-wide disaster that takes out the whole NAS.
For other larger local hosters who are smarter and more prepared, what do you do? Do you sync it off site? How do you deal with cost and bandwidth needs if so? What other backup strategies do you use?
(Sorry if this standard scenario has been discussed - searching didn’t turn up anything.)


Do you have logs or software that keeps track of what you need to redownload? A big stress for me with that method is remembering or keeping track of what is lost when I and software can’t even see the filesystem anymore.
If you can’t remember what you lost, did you really need it to begin with?
Unless it’s personal memories of course.
I can’t remember the name of an excel spreadsheet I created years ago, which has continually matured with lots of changes. I often have to search for it of the many I have for different purposes.
Trusting your memory is a naive, amateur approach.
The key here being that you actually remember the file exists, because it’s important. Some other random spreadsheet you don’t even remember exists because you haven’t needed it since forever is probably not all that important to backup.
If you loose something without ever realizing you lost it, it was not important so there would be no reason to make a backup.
If the spreadsheet is important it sounds like it would be part of the 4 GB that was backed up.