Resilience of Systems - Azure Paired Regions

The LMS365 platform is operated on a redundant infrastructure setup on Microsoft Azure operated securely in multiple geographies around the world. The availability of this system is guaranteed through the Microsoft Azure Cloud.

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 data centers.

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.

georegiondatacenter.png

Figure 1 – Azure regional pair diagram

 LMS365 Geography Paired regions
 Americas  Central US  East US 2
 Asia Pacific  Japan East  Japan West
 Australasia  Australia East  Australia Southeast
 Canada  Canada Central  Canada East
 Europe  North Europe (Ireland)  West Europe (Netherlands)
 Germany  Central Germany  Northeast Germany
 United Kingdom (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

Figure 2 – Hypothetical Azure regional pair

 

Benefits of paired regions

  1. 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.).

  2. Platform-provided replication - Some services such as Geo-Redundant Storage provide automatic replication to the paired region.

  3. 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.

  4. 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.
  5. 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 

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