How to properly organize data storage on servers?

Question

Database

There was a question how it is correct to store the data on the server? There are 4 servers. What needs to be stored: personal data of users (documents), accounting, personal data of citizens (databases of various programs). Google didn't turn up anything good.

Answer 1

1. It is necessary to store it in such a way that if data from any 3 servers disappears, then on the remaining one there will be all the data and not keep all the "eggs in one basket".
2. Of course, you need to create reliable encryption and distribution of access to data.
3. Design a fault tolerance system and provide DDoS protection.
4. Configure network security policies and packet rules.
5. Raid10 on each server - minimum.