Well, I beg to differ (what else ;-)

OpenBSD does help you, when something goes wrong:
like for example with immuteable files, or append only files, so no one can delete your logfiles! At least you have the chance to look at what the "bad guys" did. Indeed a very fine feature for a logserver, isn't it?
Or OpenBSD secure modes?
Plus, you can put your WEB-Server in a jail, so *IF* someone breaks into your WEB-Server, well, the whole system is still NOT compromised.
Jails work very well! Maybe even better the the comparative Linux stuff...

And sorry, but SELinux is such a PITA, I've never seen anyone using it, mostly it is simply disabled, because it is the root cause of many problems.

Yes, VMS was a great system, but it is even deader the the *BSDs ;-)
No, really, Application support on (Open)VMS is not so great, and Drivers for many addon-cards are noexistent. So, even if it was (is) good, it is in no way mass compatible.

To me, it seems you tried to put down OpenBSD in favor of something else (no namecalling, please!), but you failed, because your Points are rather incorrect.

But, what should I say more, be happy with whatever OS you're running and may you never be hacked.

Well, first you would need to define goals.
What do I want to backup? (only Data, or OS + Apps + Data)
Is my Data rather static or does it change a lot?
How fast does it change?
Do I have enough bandwidth to cope with the backup? (12TB is a lot! It would take more than a day to copy it over a GBit link... so, how much of the data changes over a day?)
Do i need daily backups? or even hourly?
How fast do i need to restore everything?
Do i need different versions? (Then the needed storage might be much higher than 12TB, ouch)
Who needs to restore files? (only the admins, or the users themself)

So it all boils down to: how much money do I have ;-)

Brgds
Michael