August 2019
Beginner to intermediate
232 pages
3h 50m
Chinese
Content preview from Web容量规划之美
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50
第
2
章
该服务器需要用来处理消耗很多
CPU
的工作吗？它需要执行消耗很多内存的工作
吗？对网络有很高的要求吗？
现在，水平和垂直比例架构之间的差异在业界是众所周知的，但为了将容量规划
放到上下文中（见图
2-5
），值得回顾一下：
•
能够水平扩展意味着有一个架构，只要在现有的基础设施中添加类似的功能节
点，就可以增加容量。例如，多加一个
Web
服务器分担网站访问的负担。在
水平扩展的情况下，只需要处理服务瓶颈所需的资源就需要进行扩展。水平扩
展是微服务架构的典型选择。
•
能够垂直扩展是指一种通过增加服务器内部的资源（例如
CPU
、内存、磁盘和
网络）来增加容量的能力。在集中部署体系结构中，垂直扩展是典型的选择。
图
2
-
5
：垂直与水平扩展图
随着分层架构和无共享架构的出现，作为网络应用横向扩展以其相对水平扩展的
优势受到更广泛的认可。能够横向扩展意味着设计你的应用来处理不同层次的数
据库抽象和分布。你可以在
Henderson
和
Schlossnagle
的书中找到很多关于横向扩
展应用程序开发技术的好方法。
仅仅依靠垂直扩展的弊端在于，随着你对计算机的各个部分进行升级的同时成本
显著上升。同时给你带来了单点故障的风险（
SPOF
）。当扩展服务器群的服务器
规模的时候，水平扩展涉及增加潜在故障点的更复杂的问题。此外，对于各个节
点之间的数据同步，也无疑带来了一些挑战。例如，在分布式数据库或分布式仓
51
设定容量目标
库中保证强一致性需要各个节点之间的同步。同样在多线程执行的上下文中，常
常需要线程同步来保证正确性。
对角线扩展（由 ...
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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.