Availability Zones (or AZ for short) are the core of the AWS Global Infrastructure, with 80 Availability Zones across 25 geographic locations. But what are AWS Availability Zones and where are they located?
Before understanding what an Availability Zone is, we need to understand what a Region is. In short, a region is a geographical area that houses a collection of Availability Zones that map to physical data centres within the region. Regions are physically isolated from one another; including isolation of location, power and water supply.
The physical isolation of Regions is crucial for workloads that require compliance and data sovereignty as data can be guaranteed to remain in particular geographical locations. The worldwide presence of AWS Regions is also essential for latency-sensitive workloads that need to be located near users of a particular geographic location.
Previously, Regions had a minimum of 2 Availability Zones, however moving forwards new Regions will have a minimum of 3 Availability Zones where possible. us-east-1 currently contains the most with 5 Availability Zones. We’ll touch on the importance of multiple Availability Zones later on in the article.
You’ve read all about Availability Zones within Regions, but what exactly are they? An Availability Zone is a logical data centre within a Region that can be used by an AWS Customer.
Just like Regions, each Availability Zone has its own power supply, networking and connectivity to reduce the likelihood of two zones failing simultaneously and causing downtime to the customer; this is why multiple Availability Zones per Region is important.
It’s commonly misunderstood that a single Availability Zone is or contains a single data centre. This isn’t the case, each zone contains one or more data centres that are connected via low-latency private network links. However, whilst a single Availability Zone can contain multiple data centres, no two zones share the same data centre.
Furthermore, Amazon maps Availability Zones to identifiers on each individual AWS account to evenly distribute resources. This means that the us-east-1a Availability Zone for one account may not be backed by the same data centre as another account using the same Availability Zone.
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