amazon-web-services - 为什么 AWS RDS 子网组需要多个可用区？

Question

创建新的 RDS MS SQL 实例时，它需要一个跨越多个可用区的子网组。我知道这与多 A-Z 复制不同，我的实例将存在于单个可用区域内。
那么当我添加这个跨越不同区域的子网组时，这实际上在做什么？

Answer 1

RDS 使用额外的可用区来存储备份数据和日志以实现冗余，您的实例的数据存储在其他可用区中。

更多信息可以在这里找到:

https://aws.amazon.com/rds/faqs/

Q: Why does additional backup storage cost more than allocated DB Instance storage?

The storage provisioned to your DB Instance for your primary data is located within a single Availability Zone. When your database is backed up, the backup data (including transactions logs) is geo-redundantly replicated across multiple Availability Zones to provide even greater levels of data durability. The price for backup storage beyond your free allocation reflects this extra replication that occurs to maximize the durability of your critical backups.