Azure operates in multiple geographies around the world. An Azure geography is a defined area of the world that contains at least one Azure Region. An Azure region is an area within a geography, containing one or more datacenters.
To ensure Business continuity and disaster recovery (BCDR) each Azure region is paired with another region within the same geography, together making a regional pair.
Figure 1 – Azure regional pair diagram
|LMS365 Geography||Paired regions|
|Asia Pacific||Japan East||Japan West|
|Australasia||Australia East||Australia Southeast|
|Canada||Canada Central||Canada East|
|Germany||Central Germany||Northeast Germany|
|Europe||North Europe (Ireland)||West Europe (Netherlands)|
|North America||Central US||East US 2|
|UK||UK South||UK West|
|US Government||US Gov Virginia||US Gov Texas|
An example of paired regions
Figure 2 below shows a hypothetical application that uses the regional pair for disaster recovery. The green numbers highlight the cross-region activities of three Azure services (Azure compute, storage, and database) and how they are configured to replicate across regions. The unique benefits of deploying across paired regions are highlighted by the orange numbers.
Figure 2 – Hypothetical Azure regional pair
Benefits of paired regions
- Physical isolation – When possible, Azure prefers at least 300 miles of separation between datacenters in a regional pair, although this isn't practical or possible in all geographies. Physical datacenter separation reduces the likelihood of natural disasters, civil unrest, power outages, or physical network outages affecting both regions at once. Isolation is subject to the constraints within the geography (geography size, power/network infrastructure availability, regulations, etc.).
- Platform-provided replication - Some services such as Geo-Redundant Storage provide automatic replication to the paired region.
- Region recovery order – In the event of a broad outage, recovery of one region is prioritized out of every pair. Applications that are deployed across paired regions are guaranteed to have one of the regions recovered with priority. If an application is deployed across regions that are not paired, recovery might be delayed – in the worst case the chosen regions may be the last two to be recovered.
- Sequential updates – Planned Azure system updates are rolled out to paired regions sequentially (not at the same time) to minimize downtime, the effect of bugs, and logical failures in the rare event of a bad update.
- Data residency – A region resides within the same geography as its pair (with the exception of Brazil South) to meet data residency requirements for tax and law enforcement jurisdiction purposes.
More Information see: https://docs.microsoft.com/en-us/azure/best-practices-availability-paired-regions