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<td width="100%" align="center" height="53" colspan="2"><font size="5" face="黑体" color="#FFFFFF"><font LANG="ZH-CN">第九章</font>
</font><font size="5" face="黑体" color="#FFFFFF">操作系统引论</font></td>
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<p align="center"><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF"><a href="#ch91">9．1<span style="mso-spacerun: yes">
</span>磁盘I/O</a><o:p>
</o:p>
</font></span></p>
<p align="center"><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF"><a href="#ch92">9．2<span style="mso-bidi-font-size: 10.0pt">
</span>外存分配方法</a><o:p>
</o:p>
</font></span></p>
<p align="center"><font color="#FFFFFF"><span lang="EN-US"><a href="#ch93"><span style="mso-bidi-font-size: 10.0pt">9．3
空闲存储空间的管理</span></a></span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p align="center"><font color="#FFFFFF"><span lang="EN-US"><a href="#ch94"><span style="mso-bidi-font-size: 10.0pt">9．4
磁盘容错技术</span></a></span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p align="center"><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><font color="#FFFFFF"><a href="#ch95">9．5<span style="mso-bidi-font-size: 10.0pt">
</span>文件系统的性能改善</a><o:p>
</o:p>
</font></span></p>
<p align="center"><font color="#FFFFFF"><span lang="EN-US"><a href="#ch96"><span style="mso-bidi-font-size: 10.0pt">9．6
数据一致控制</span></a></span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p style="TEXT-ALIGN: center" align="center"> </td>
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<td width="18%" align="center" height="39"><font LANG="ZH-CN" color="#FFFFFF">作业：</font></td>
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<p align="left"><font LANG="ZH-CN" color="#FFFFFF"> </font></td>
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<td width="114%" align="center" height="39" colspan="2"><a href="index.htm"><font color="#FFFFFF">返回<<</font></a></td>
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<p align="center"><font color="#FFFFFF"> <span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><a name="ch91"></a>9．1<span style="mso-spacerun: yes">
</span>磁盘I/O<o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">提高磁盘</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt">I/O</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">速度的主要途径：</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US"> </span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑴选择性能好的磁盘；</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US"> </span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑵采用好的磁盘调度算法</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US"> </span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑶设置磁盘高速缓冲区</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p style="MARGIN-LEFT: 18pt; TEXT-INDENT: -18pt; tab-stops: list 18.0pt; mso-list: l30 level1 lfo29"><font color="#FFFFFF"><span lang="EN-US" style="mso-fareast-font-family: 黑体">1．</span><span style="mso-ascii-font-family: Times New Roman">磁盘性能简述</span><span lang="EN-US" style="mso-fareast-font-family: 黑体"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US"> </span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑴数据组织——标识符字段、数据字段</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US"> </span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑵磁盘类型——固定头磁盘：每条磁道有一个读</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt">/</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">写磁头</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US">
</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">移动头磁盘：每一个盘面仅配有一个磁头</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US"> </span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑶磁盘访问时间</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US">
</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">寻道时间：把磁头从当前位置移动到指定磁道上所经历的时间。</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US">
</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">旋转延迟时间：指定扇区移动到磁头下面所经历的时间</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes; mso-bidi-font-size: 10.0pt" lang="EN-US">
</span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">传输时间：把数据从磁盘读出，或向磁盘写入数据所经历的时间</span></font></p>
<p style="MARGIN-LEFT: 18pt; TEXT-INDENT: -18pt; tab-stops: list 18.0pt; mso-list: l30 level1 lfo29"><font color="#FFFFFF"><span lang="EN-US" style="mso-fareast-font-family: 黑体">2．</span><span style="mso-ascii-font-family: Times New Roman">早期的磁盘调度算法：</span><span lang="EN-US" style="mso-fareast-font-family: 黑体"><o:p>
</o:p>
</span></font></p>
<p><font color="#FFFFFF"><span style="mso-spacerun: yes" lang="EN-US"> </span><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">⑴先来先服务：</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p style="TEXT-INDENT: 24pt"><font color="#FFFFFF"><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">根据进程访问磁盘的时间顺序先来先服务</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p style="TEXT-INDENT: 24pt"><font color="#FFFFFF"><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">优点：公平、简单</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
</o:p>
</span></font></p>
<p style="TEXT-INDENT: 24pt"><font color="#FFFFFF"><span style="mso-bidi-font-size: 10.0pt; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">缺点：效率低</span><span lang="EN-US" style="mso-bidi-font-size: 10.0pt"><o:p>
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