《Operating System Concepts》学习第 66 天，p764-p766 总结，总计 3 页。

一、技术总结

1.cache-update policy

(1)write-through policy

In caching, a policy whereby writes are not cached but are written through the cache to the master copy of the data.

缺点：However, this policy requires each write access to wait until the information is sent to the server, so it causes poor write performance.

(2)write-back(delayed-write policy)

In caching, a policy whereby data are first written to a cache; later, the cache writes the change to the master copy of the data.

缺点：Unfortunately, delayed-write schemes introduce reliability problems, since unwritten data are lost whenever a user machine crashes.

(3)write-on-close policy

In caching, a policy whereby writes reside in the cache until the file is closed and are only then written back to the master copy of the data.

二、英语总结(生词：2)

1.replication

(1)replicate：re-("again") + plicare("to fold")

vi/vt. replicate literally means "to fold back", overtime, it evolves to mean "to make or do sth again(复现)"。

(2)replication

c/u. the act of making or doing sth again。

(3)示例

To enhance the availability of the crucial mapping information, we can use replication, local caching, or both(《Operating System Concepts》第 764 页)。

2.granularity

(1)granularity: gran("grain，颗粒") + -ul(a diminutive suffix, "small") + -ity(a noun suffix, "quality of")

u. the quality of including a lot of small details(粒度)。

(2)示例

The granularity of the cached data in a DFS can vary from blocks of a file to an entire file(《Operating System Concepts》第 765 页)。

关于英语的注解同步更新汇总到 https://github.com/codists/English-In-CS-Books 仓库。

三、其它

今天没有什么想说的。

四、参考资料

1. 编程

(1) Abraham Silberschatz，Peter Baer Galvin，Greg Gagne《Operating System Concepts》：https://book.douban.com/subject/30272539/

2. 英语

(1) Etymology Dictionary：https://www.etymonline.com

(2) Cambridge Dictionary：https://dictionary.cambridge.org

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