为什么子网不能跨越 AWS 中的可用区? [英] Why can't a subnet span availability zones in AWS?

问题描述

在 AWS 中，一个 VPC 子网只能驻留在一个可用区中.我很好奇这个限制背后的原因是什么.

In AWS a VPC subnet can only reside in one availability zone. I'm curious what's the reason behind this restriction.

我不知道 AWS 如何在幕后实现 VPC.但是通常VPC的实现是基于overlay网络的，比如VXLAN.以 VXLAN 为例，从技术上讲，虚拟子网中的两个端点可以通信，只要托管端点的两个物理主机可以通信.这两个主机是否在可用区中无关紧要.

I don't know how AWS implements VPC under the hood. But usually VPC implementation is based on overlay network, such as VXLAN. Take VXLAN as an example, technically two endpoints in a virtual subnet can communicate as long as the two physical hosts hosting the endpoints can communicate. It shouldn't matter whether these two hosts are in an availability zone or not.

所以我想知道限制的原因是什么.是因为性能还是其他一些网络限制?

So I'm wondering what's the reason for the limitation. Is it due to performance or some other network limitations?

推荐答案

这是设计使然，子网关联指示您的资源位于哪个可用区.

This is by design, a subnet association is the indicator of which availability zone your resource is located in.

对于提高弹性和高可用性的计划，用户确保其资源之间存在隔离至关重要.如果一个子网可以跨越多个可用区，那么您就无法保证它们的基础设施会因断电等原因全部瘫痪.

For planning to improve resilience and high availability, it is key for the user to guarantee there is isolation between their resources. If a subnet could span several availability zones then you could not guarantee that their infrastructure could all be brought down by a power cut for example.

另一方面，有些人希望保证其 VPC 环境中资源之间的延迟最小.通过将它们全部部署到同一个子网，他们可以保证流量将保持在同一个逻辑数据中心内，这将为他们提供服务之间的最佳延迟.

On the other hand some people want to guarantee the minimum latency between resources within their VPC environment. By deploying them all to the same subnet they can guarantee that traffic will remain inside of the same logical data centre which will provide them the best latency between services.

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