哪位好心的老大给帮忙看看这题是啥意思，红皮书183上的一道题。

xisanqi

哪位好心的老大给帮忙看看这题是啥意思，红皮书183上的一道题。
A.我知道是对的
B.我不清楚
C.并行写要等最长的写完才写后面的
D.顺序写不用等前面的写没写完就可以写后面的
不知我理解的对不对，书上给的答案选D，但对于并行写和顺序写我还是不太清楚哪位老大能给讲讲，先谢了！

9. A system administrator is trying to develop a logical volume strategy based on
availability, performance, and cost that is appropriate to the site. Which of the
following statements is not true?
A. Performance is the average speed at which data is accessed. Policies
such as write-verify and mirroring add to system processing load, and
thus degrade performance.
B. Specifying mirrored logical volumes with a parallel-scheduling policy may
improve I/O read-operation performance because multiple copies allow
the system to direct the read operation to the copy that can be most
quickly accessed.
C. The parallel-scheduling policy starts the write operation for all the
physical partitions in a logical partition at the same time. When the write
operation to a partition that takes the longest to finish is complete, the
write operation is considered complete.
D. The sequential-scheduling policy performs writes to multiple copies or
mirrors in order. In sequential scheduling, the physical partitions are
written to in sequence. The system does not wait for the write operation
to complete before starting the write operation for the next one.

ar6400

顺序写：每个copy写完后才写下一个。故此处的D是错的。

树袋熊

偶来砍你一刀：
A：你知道是对的，偶就不说了。
B：做磁盘镜相的时候，写是同时写两个磁盘，速度基本变化不大，但读的时候，因为有两个地方存在相同的信息 ，可以随即的读到，所以提高了读的性能，这个是以浪费磁盘空间为代价换来的安全和读性能的提高。
C：你明白我就不说了。
D：顺序写，当然要结束前一个才能写后一个，而这个是说不用结束就写下一个了，所以这个是错误的说法，那答案该是这个。
183是那本书我不知道，但这个题书你看了仔细的话，就一定能答对。

183是手机器性能的吗？还是系统支持的？
我有时间的时候一定翻翻这本书。



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