November 2020
Beginner to intermediate
214 pages
5h 10m
Chinese
Content preview from 数据库可靠性工程：数据库系统设计与运维指南
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18
｜
第
2
章
可用性
SLO
样例的迭代版本如下。
•
一周内的可用性为
99.9%
。
•
单次故障不超过
10.08
分钟。
•
如果超过
5%
的用户受影响，则视为宕机。
•
允许每年
4
小时的宕机时间，如果：
–
至少提前两周与用户沟通；
–
每次影响不超过
10%
的用户。
2.3.3
吞吐量指标
作为服务级别指标，吞吐量应该列出服务必须能够支持的峰值，同时保持与其对应的延时
和可用性
SLO
。你可能会说：“莱恩和夏丽蒂，为什么还需要吞吐量指标呢？难道延时和
可用性还不够吗？”我们中的一个会这样回答：“无畏的新手，问得好！”然后她会若有
所思地吸起烟斗……
有时可能会出现瓶颈，给吞吐量设置了上限，但不至于影响性能或可用性。也许系统中存
在锁，限制系统每秒
50
个查询。这种响应可能很快，但是如果有
1000
人等待运行该查
询，就有问题了。因为有时无法测量端到端的延时，所以吞吐量指标通常可以作为系统是
否满足业务需求的一种额外验证。
当使用平均值和更粗粒度的样本时，吞吐量可能会遇到类似于延时的可见性问题，监控时
需要记住这一点。
1.
成本
/
效率指标
当考虑系统成本的有效指标时，最大的变量是采用什么指标来考量成本。这实际上是一个
业务决策，但是你应该选择在服务中驱动价值的因素。如果你是在线杂志之类的内容提供
者，那么交付的页面至关重要；如果你是软件即服务（
SaaS
）平台提供商，那么服务订阅
指标是有意义的；如果你是零售商，则交易量是合适的指标。
2.
注意事项
数据库工程师为什么需要知道这些？你管理的是服务的一个组件，为何必须关注整体需
求？在故障频发的日子里，可能已经为你设定了数据存储目标 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.