An availability zone (AZ) is a physical zone that has an independent power grid and an independent network that are isolated from each other. An AZ is a collection of one or more physical data centers that are equipped with independent air conditioning and cooling, fire protection, waterproofing and moisture protection, and electric power supply systems. Multiple AZs in a region are interconnected by high-speed optical fibers to meet the needs of users to build HA systems across AZs.
To select an AZ, please refer to the following criteria:
Within the same region, there is internal network communication between Availability Zones. Fault isolation can be achieved between different Availability Zones, meaning that if one AZ experiences a fault, it will not affect the normal operation of other AZs. Whether to place instances within the same Availability Zone depends primarily on your application's requirements for disaster recovery capabilities and network latency.
If your application requires high disaster recovery capabilities, it is recommended that you deploy instances across different Availability Zones within the same region.
If your application requires low network latency between instances, it is recommended that you create instances within the same Availability Zone.