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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239
第 14章
分片简介
本章介绍如何扩展
MongoDB
，包括：
•
分片和集群组件；
•
如何配置分片；
•
分片与应用程序的交互。
14.1
什么是分片
分片
是指跨机器拆分数据的过程，有时也会用术语
分区
（
partitioning
）来表示这个概念
。
通过在每台机器上放置数据的子集，无须功能强大的机器，只使用大量功能稍弱的机器，
就可以存储更多的数据并处理更多的负载。分片还可以用于其他目的，包括将经常访问的
数据放置在更高性能的硬件上，或基于地理位置（比如，基于在一个特定语言环境下的用
户）来拆分集合中的文档以使它们接近最常对其进行访问的应用程序服务器。
大部分数据库软件支持进行手动分片。使用这种方法，应用程序会维护到多个不同数据库
服务器端的连接，每个服务器端都是完全独立的。应用程序不仅管理不同服务器上不同数
据的存储，还管理在适当的服务器上查询数据。这种方式可以很好地工作，但当从集群中
添加或删除节点，或者面对数据分布或负载模式的变化时，就非常难以维护了。
MongoDB
支
持自动分片，这种方式试图将数据库架构从应用程序中抽象出来，并简化系
统管理。在某种程度上，
MongoDB
允许应用程序好像始终在和一台单机的
MongoDB
服务
器对话一样。在运维方面，
MongoDB
可以自动均衡分片上的数据
，使容量的添加和删除
变得更容易。
无论从开发还是运维的角度来看，分片都是最复杂的
MongoDB
配置方式
。有许多组件需
要配置和监控，数据在集群中会自动转移。在尝试部署或使用分片集群之前，应该首先
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.