# What Azure Is and How It Is Laid Out — Azure

Source: https://www.skillbyai.com/en/azure/f-cloud

> Explain regions, availability zones and region pairs, and pick a region for a workload.

## A global set of datacentres you rent by the minute

**Microsoft Azure** is a public cloud: compute, storage, databases, networking and managed services that you create through an API and pay for as you use them. Physically, Azure is organised into **regions** (a set of datacentres in one metro area, such as *Central India* in Pune or *West Europe* in the Netherlands). Many regions have **availability zones**: at least three physically separate locations inside the region, each with independent power, cooling and networking. Spreading copies of a workload across zones protects you from one datacentre failing. Many regions also have a **paired region** in the same geography, used for platform updates that are rolled out one region of the pair at a time and for geo-replicated storage. Choosing a region is a real decision: latency to users, data-residency law, which services and VM sizes are available there, and price all differ.

## From geography to zone

Think in three levels: a geography contains regions, and a region contains availability zones.

![Nested shapes: a large area holding two regions, each region holding three smaller zone blocks.](assets/figures/azure/section-1-map.svg) — Figure 1.1 — Geography, region and availability zones.

## Listing regions from the CLI

The Azure CLI can tell you which regions your subscription can use. Names such as `centralindia` are what you pass to `--location`.

```bash
# sign in (opens a browser or device-code flow)
az login

# list regions available to the current subscription
az account list-locations --query "[].{name:name, display:displayName}" -o table

# check which VM sizes a region offers before you commit to it
az vm list-skus --location centralindia --resource-type virtualMachines -o table
```

## Region choice is hard to undo

Most resources cannot be moved to another region; you recreate them and migrate data. Decide on region up front: put resources close to users, check the service is offered there, and check whether the region has availability zones before you design for zone redundancy.

**Quiz:** What is an availability zone?

- [x] A physically separate location inside a region with independent power, cooling and network
- [ ] A paired region in another country
- [ ] A billing boundary for a team
- [ ] A virtual network inside a subscription

*Answer:* A physically separate location inside a region with independent power, cooling and network. Zones are separate datacentre locations inside one region, so a zone-redundant design survives one location failing.