《Operating System Concepts》學習第 66 天，p764-p766 總結，總計 3 頁。

一、技術總結

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.

缺點：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.

缺點：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、英語總結(生詞：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(復現)"。

(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 頁)。

2.granularity

(1)granularity: gran("grain，顆粒") + -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 頁)。

關于英語的注解同步更新匯總到 https://github.com/codists/English-In-CS-Books 倉庫。

三、其它

今天沒有什么想說的。

四、參考資料

1. 編程

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

2. 英語

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

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

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