What is the main advantage of using fault domains in OCI?

The main advantage of using fault domains in Oracle Cloud Infrastructure (OCI) is that they protect your instances from power supply failures. Fault domains are logical groupings of hardware in an OCI region that help ensure high availability by isolating the hardware resources from each other. By distributing instances across different fault domains, you minimize the risk that a localized hardware failure (such as a problem with power supply, cooling, or networking within one fault domain) will impact all of your instances.

The design of fault domains enables a multi-layered approach to redundancy. When applications are deployed across multiple fault domains, they can continue to function even if one domain encounters an issue, thus enhancing the overall resiliency of your cloud architecture.

In contrast, low-latency connections across regions pertain more to network architecture than to fault domains. Bandwidth allocation per domain is not a function of fault domains; rather, it relates to network management and configuration. Lastly, fault domains do not ensure instances are only placed in a single data center; instead, they help distribute instances across different physical infrastructure within a single data center, which supports high availability and fault tolerance.