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Date: Mon, 11 Nov 1996 17:25:03 GMTServer: NCSA/1.5Content-type: text/htmlLast-modified: Thu, 25 Apr 1996 13:55:34 GMTContent-length: 2641<html><head><title>CS 537 - Quiz #9</title></head><body><table border=0 width=100% align=center><tr><td width=25%><td width=50% align=center><b>UNIVERSITY OF WISCONSIN-MADISON<br>Computer Sciences Department</b><td width=25%><tr><tr><td><b>CS 537<br>Spring 1996 </b><td><td align=right><b>Bart Miller</b><tr><td><td align=center><b>Quiz #9</b><br>Wednesday, April 24<td></table><h2>File Systems</h2><h3>1. Unix File Sizes</h3>Consider the old UNIX file system (Version 7 or 4.1BSD).Assume that disk blocks are 1K bytes and each pointer to a disk blockrequires 4 bytes.What is the largest possible file using this design.Show your work (as an expression) to make sure you get credit;if your expression is correct, you will get full credit.<b><p>The old UNIX file system has 10 direct pointers to data blocks in the i-node,plus a pointer to a single-indirect block that contains pointers to 256additional data blocks,plus a pointer to a double-indirect block that contains pointers to 256blocks that each contain pointers to 256 additional data blocks,plus a pointer to a triple-indirect block that contains pointers to 256blocks that each contain pointers to 256blocks that each contain pointers to 256 additional data blocks:<p></b><center><table><tr><td>Data blocks pointed to by i-node: <td align=right>10<tr><td>Data blocks pointed to by single-indirect block: <td align=right>+ 256<tr><td>Data blocks pointed to by double-indirect block: <td align=right>+ 256 * 256<tr><td>Data blocks pointed to by triple-indirect block: <td align=right>+ 256 * 256 256<tr><td colspan=2><hr><tr><td><b>Total Number of Blocks:</b> <td align=right><b>16,843,018</b><tr><td colspan=2><hr><tr><td>Number of bytes per block:: <td align=right>x 1,024<tr><td><b>Total Number of Bytes:</b> <td align=right><b>17,247,250,432</b><tr><td colspan=2><hr></table></center><h3>2. Unix File Access Speed</h3>Assume that you have the Unix file system presented above in Problem 1.Also assume that the operating system has already read the i-node foryour file into memory (RAM).How many <i>additional</i> disk reads will be required to read data blocknumber 300 into memory?To assure full credit, list each additional disk read.<b><p>Three (3) additional reads are necessary:<ol><li>Read the first indirect block for double indirection.<li>Read the second indirect block (for blocks 267-522)<li>Read the data block for block 300.</ol></b><hr><H4>Last modified:Thu Apr 25 08:52:12 CDT 1996by<a href="http://www.cs.wisc.edu/~bart">bart</a></b></H4></body>⌨️ 快捷键说明
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