Regions and Availability Zones

 Amazon EC2 is hosted in multiple locations world-wide. These locations are composed of AWS Regions, Availability Zones, Local Zones, AWS Outposts, and Wavelength Zones.

  • Each Region is a separate geographic area.

  • Availability Zones are multiple, isolated locations within each Region.

  • Local Zones provide you the ability to place resources, such as compute and storage, in multiple locations closer to your end users.

  • AWS Outposts brings native AWS services, infrastructure, and operating models to virtually any data center, co-location space, or on-premises facility.

  • Wavelength Zones allow developers to build applications that deliver ultra-low latencies to 5G devices and end users. Wavelength deploys standard AWS compute and storage services to the edge of telecommunication carriers' 5G networks.

AWS operates state-of-the-art, highly available data centers. Although rare, failures can occur that affect the availability of instances that are in the same location. If you host all of your instances in a single location that is affected by a failure, none of your instances would be available.

Regions

Each Region is designed to be isolated from the other Regions. This achieves the greatest possible fault tolerance and stability.

When you view your resources, you see only the resources that are tied to the Region that you specified. This is because Regions are isolated from each other, and we don't automatically replicate resources across Regions.

When you launch an instance, you must select an AMI that's in the same Region. If the AMI is in another Region, you can copy the AMI to the Region you're using.

Availability Zones

Each Region has multiple, isolated locations known as Availability Zones. The code for Availability Zone is its Region code followed by a letter identifier. For example, us-east-1a.

When you launch an instance, you select a Region and a virtual private cloud (VPC), and then you can either select a subnet from one of the Availability Zones or let us choose one for you. If you distribute your instances across multiple Availability Zones and one instance fails, you can design your application so that an instance in another Availability Zone can handle requests. You can also use Elastic IP addresses to mask the failure of an instance in one Availability Zone by rapidly remapping the address to an instance in another Availability Zone. （如果您将实例分布在多个可用区并且一个实例出现故障，您可以设计您的应用程序，以便另一个可用区中的实例可以处理请求。 您还可以使用弹性 IP 地址通过快速将地址重新映射到另一个可用区中的实例来掩盖一个可用区中的实例的故障。）

The following diagram illustrates multiple Availability Zones in an AWS Region. Availability Zone A and Availability Zone B each have one subnet, and each subnet has instances. Availability Zone C has no subnets, therefore you can't launch instances into this Availability Zone.      

子网/VPC可以跨AZ（可用区），不可以跨Region（区域）。

A Region with instances in one Availability Zone.

As Availability Zones grow over time, our ability to expand them can become constrained. If this happens, we might restrict you from launching an instance in a constrained Availability Zone unless you already have an instance in that Availability Zone. Eventually, we might also remove the constrained Availability Zone from the list of Availability Zones for new accounts. Therefore, your account might have a different number of available Availability Zones in a Region than another account.

随着可用区随着时间的推移而增长，我们扩展它们的能力可能会受到限制。 如果发生这种情况，我们可能会限制您在受限可用区中启动实例，除非您在该可用区中已有实例。 最终，我们可能还会从新账户的可用区列表中删除受限可用区。 因此，您的账户在一个区域中的可用可用区数量可能与另一个账户不同。

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