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Update 计算机操作系统 - 设备管理.md

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重新绘制配图，补充磁盘调度的示例。
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CyC2018
2026-10-26 22:04:15 +08:00
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commit f7f18ae190
5 changed files with 184 additions and 2 deletions
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notes/pics/disk-scan.png
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notes/计算机操作系统 - 设备管理.md
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## 磁盘调度算法
下面的例子中，磁头当前位于 50 号磁道，按到达顺序有 72、30、95、56、12、81、44 七个请求。先来先服务按这个顺序移动，共移动 318 个磁道。
读写一个磁盘块的时间的影响因素有：
- 旋转时间（主轴转动盘面，使得磁头移动到适当的扇区上）
@@ -46,7 +48,7 @@
虽然平均寻道时间比较低，但是不够公平。如果新到达的磁道请求总是比一个在等待的磁道请求近，那么在等待的磁道请求会一直等待下去，也就是出现饥饿现象。具体来说，两端的磁道请求更容易出现饥饿现象。
<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/4e2485e4-34bd-4967-9f02-0c093b797aaa.png"/> </div><br>
<div align="center"> <img src="pics/disk-sstf.png" width="760px"/> </div><br>
### 3. 电梯算法
@@ -58,4 +60,4 @@
因为考虑了移动方向，因此所有的磁盘请求都会被满足，解决了 SSTF 的饥饿问题。
<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/271ce08f-c124-475f-b490-be44fedc6d2e.png"/> </div><br>
<div align="center"> <img src="pics/disk-scan.png" width="760px"/> </div><br>
tools/diagram/src/disk-scan.svg
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