Reliability terminology

To better understand regions and availability zones in Azure, it helps to understand key terms or concepts.

Term	Definition
Region	A geographic perimeter that contains a set of datacenters.
Datacenter	A facility that contains servers, networking equipment, and other hardware to support Azure resources and workloads.
Availability zone	[A separated group of datacenters within a region.][availability-zones-overview] Each availability zone is independent of the others, with its own power, cooling, and networking infrastructure. [Many regions support availability zones.][azure-regions-with-availability-zone-support]
Paired regions	A relationship between two Azure regions. [Some Azure regions][azure-region-pairs] are connected to another defined region to enable specific types of multi-region solutions. [Newer Azure regions aren't paired.][regions-with-availability-zones-and-no-region-pair]
Region architecture	The specific configuration of the Azure region, including the number of availability zones and whether the region is paired with another region.
Locally redundant deployment	A deployment model in which a resource is deployed into a single region without reference to an availability zone. In a region that supports availability zones, the resource might be deployed in any of the region's availability zones.
Zonal (pinned) deployment	A deployment model in which a resource is deployed into a specific availability zone.
Zone-redundant deployment	A deployment model in which a resource is deployed across multiple availability zones. Microsoft manages data synchronization, traffic distribution, and failover if a zone experiences an outage.
Multi-region deployment	A deployment model in which resources are deployed into multiple Azure regions.
Asynchronous replication	A data replication approach in which data is written and committed to one location. At a later time, the changes are replicated to another location.
Synchronous replication	A data replication approach in which data is written and committed to multiple locations. Each location must acknowledge completion of the write operation before the overall write operation is considered complete.
Active-active	An architecture in which multiple instances of a solution actively process requests at the same time.
Active-passive	An architecture in which one instance of a solution is designated as the primary and processes traffic, and one or more secondary instances are deployed to serve traffic if the primary is unavailable.