November 2021
Intermediate to advanced
410 pages
12h 1m
Chinese
Content preview from MongoDB权威指南（第3版）
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240
｜
第
14
章
熟悉单机服务器和副本集。此外，与副本集一样，配置和部署分片集群的推荐方式是通
过
MongoDB
Ops Manager
或
MongoDB Atlas
。如果需要保留对计算基础设施的控制，建议
使用
Ops
Manager
。如果可以将基础设施管理留给
MongoDB
（可以选择在
Amazon AWS
、
Microsoft Azure
或
Google Compute Cloud
中运行）
，则推荐使用
MongoDB Atlas
。
14.2
理解集群组件
MongoDB
的分片机制允许你创建一个由许多机器（分片）组成的集群，并将集合中的数
据分散在集群中，在每个分片上放置数据的一个子集。这允许应用程序超出单机服务器或
副本集的资源限制。
许多人对复制和分片之间的区别感到困惑。记住，复制在多台服务器上创建
了数据的精确副本，因此每台服务器都是其他服务器的镜像。相反，每个分
片包含了不同的数据子集。
分片的目标之一是使由两个、
3
个、
10
个甚至数百个分片组成的集群对应用程序来说就像
是一台单机服务器。为了对应用程序隐藏这些细节，需要在分片前面运行一个或多个称为
mongos
的路由进程
。
mongos
维护着一个“目录”，指明了哪个分片包含哪些数据。如图
14-1
所示
，应用程序可以正常连接到此路由服务器并发出请求。路由服务器知道哪些数据
在哪个分片上，可以将请求转发到适当的分片。如果有对请求的响应，路由服务器会收集
它们，并在必要时进行合并，然后再发送回应用程序。对应用程序来说，它只知道自己连
接到了一个单独的
mongod
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