How to choose: answering the main questions
What does an HA cluster consist of?
Minimum: 2–3 identical nodes, 10/25GbE network between them, shared storage (SAN/Ceph/ZFS replication), and quorum. Virtual machines are automatically restarted on healthy nodes if one fails.
Two nodes or three?
Three is the correct quorum for true Ceph. Two nodes + an external witness is a budget compromise for small businesses; we design for both options.
DBMS cluster separately?
Yes, databases are clustered using their own tools (PostgreSQL streaming, AlwaysOn) on top of or instead of hypervisor HA — this way RPO approaches zero. We select the scheme for your DBMS.