A rack defines a failure domain. A failure domain can be a region’s availability zone (zone), or a cluster node (host). A resource set can be mapped to a rack. For example, to guarantee high availability over different availability zones, multiple resource sets are created in different racks. You can also enforce affinity and anti-affinity rules to minimize cross-AZ traffic.

When a resource set is mapped to a rack, all the resource set’s replicas will be placed in the same failure domain.

To use a rack, assign it to a resource set: