“多可用区部署"的区别和“只读副本版本多可用区部署" [英] Difference between "Multi-AZ Deployment" and "Read Replica Verison Multi-AZ Deployment"
问题描述
Amazon RDS 有两种主要不同类型的副本，多可用区副本和只读副本，很容易找到它们的区别.
Amazon RDS has two main different types of replicas, Multi-AZ Replica and Read Replica, and it's easily to find their difference.
但是，只读副本已在 2018 年 1 月支持多可用区部署.
However, Read Replica had supported Multi-AZ deployment at JAN, 2018.
多可用区部署"和只读副本版本多可用区部署"的主要区别是什么?
实例操作
→ 修改
→ 指定多可用区部署"选项
Instance Action
→ Modify
→ specified the "Multi-AZ deployment" option
实例操作
→ 创建只读副本
→ 指定多可用区部署"选项
Instance Action
→ Create read replica
→ specified the "Multi-AZ deployment" option
推荐答案
RDS 只读副本 实例是上游主(主")数据库实例的异步只读副本.您的应用程序可以将它用于任何不需要更改数据的查询，从而减轻主服务器的负载.如果副本崩溃或失败，它不会对主服务器产生影响，但副本本身无法再处理任何流量.
An RDS read replica instance is an asynchronous read-only replica of an upstream primary ("master") database instance. It can be used by your application for any query that does not require changing data, thus relieving load from the master. If the replica crashes or fails, it has no impact on the master but the replica itself can no longer handle any traffic.
Multi-AZ是指数据库实例在同一区域的不同可用区有一个备用的备用服务器机器和备用硬盘.这是一个同步副本，但您无法访问.如果活动服务器出现故障，备用服务器会接管并开始处理流量，这比没有备用服务器时可能更快.
Multi-AZ means the database instance has a standby spare server machine and spare hard drive in a different availability zone of the same region. This is a synchronous replica, but cannot be accessed by you. If the active server fails, the spare server takes over and starts handling traffic more quickly than would be possible without the spare.
多可用区是一种提高可靠性的部署策略.它减少了版本升级所需的停机时间，并减少了备份快照和副本创建的影响，因为快照可以从备件(由服务)完成.由于它提供了热备容量，它使实例的成本增加了一倍.
Multi-AZ is a deployment strategy for higher reliability. It reduces the downtime required for version upgrades, and reduces the impact of backup snapshots and creation of replicas, since snapshots can be done from the spare (by the service). It doubles the cost of the instance because of the hot standby capacity it provides.
多可用区通常仅用于主实例，以实现快速恢复.
从历史上看，这是多可用区的唯一变体，但现在可以使用多可用区只读副本，这听起来像:具有多可用区的副本.因为它有备用硬件，它会更快地从故障和故障中恢复.活动和备用是彼此的同步副本，但仍然是主的异步副本，因为所有非 Aurora 副本都在 RDS/MySQL 中.
Historically, this was the only variant of Multi-AZ, but a Multi-AZ read replica is now possible, and is what it sounds like: a replica with Multi-AZ. It will recover more quickly from faults and failures because it has spare hardware. The active and spare are synchronous replicas of each other but are still asynchronous replicas of the master, as all non-Aurora replicas are in RDS/MySQL.
将只读副本与多可用区相结合，您可以构建弹性灾难恢复策略并简化数据库引擎升级过程.
Combining Read Replicas with Multi-AZ enables you to build a resilient disaster recovery strategy and simplify your database engine upgrade process.
Amazon RDS 只读副本使您能够在同一 AWS 区域或不同 AWS 区域中创建数据库实例的一个或多个只读副本.然后，对源数据库所做的更新异步复制到您的只读副本.除了为读取密集型工作负载提供可扩展性之外，只读副本还可以在需要时提升为独立的数据库实例.
Amazon RDS Read Replicas enable you to create one or more read-only copies of your database instance within the same AWS Region or in a different AWS Region. Updates made to the source database are then asynchronously copied to your Read Replicas. In addition to providing scalability for read-heavy workloads, Read Replicas can be promoted to become a standalone database instance when needed.
总而言之，主服务器上的多可用区为您提供一台带有不可见热备件的服务器，用于故障恢复，但不是可用的数据库副本.这是一个很好的弹性策略.
In summary, Multi-AZ on the master gets you one server with an invisible hot spare that is used for failure recovery but is not a usable database replica. It is a good strategy for resiliency.
副本上的多可用区是一种加快崩溃实例恢复时间的昂贵方法.它是一个单独的服务器，因此您可以访问，但非多可用区只读副本也可以访问.
Multi-AZ on a replica is an expensive way of speeding recovery time on a crashed instance. It is a separate server, so can be accessed by you, but so can a non-Multi-AZ read replica.
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