Midterm Exam - Stanford Secure Computer Systems Group
Midterm Exam - Stanford Secure Computer Systems Group Midterm Exam - Stanford Secure Computer Systems Group
– p. 2/16 Back in the 80s. . . • Disks spin at 3,600 RPM - 17 ms/Rotation (vs. 4 ms on fastest disks today) • Fixed # sectors/track (no zoning) • Head switching free () • Requests issued one at a time - No caching in disks - Head must pass over sector after getting a read - By the time OS issues next request, too late for next sector • Slower CPUs, memory - Noticeable cost for block allocation algorithms
– p. 3/16 Original Unix file system • Each FS breaks partition into three regions: - Superblock (parameters of file system, free ptr) - Inodes – type/mode/size + ptr to data blocks - File and directory data blocks • All data blocks 512 bytes • Free blocks kept in a linked list
- Page 1: - p. 1/16 Midterm Exam • Reminder
- Page 5 and 6: - p. 5/16 Problems with original FS
- Page 7 and 8: - p. 7/16 FFS superblock • Contai
- Page 9 and 10: - p. 9/16 Inode allocation • Allo
- Page 11 and 12: - p. 11/16 Block allocation • Try
- Page 13 and 14: - p. 13/16 Updating FFS for the 90s
- Page 15 and 16: - p. 15/16 Ordering of updates •
– p. 2/16<br />
Back in the 80s. . .<br />
• Disks spin at 3,600 RPM<br />
- 17 ms/Rotation (vs. 4 ms on fastest disks today)<br />
• Fixed # sectors/track (no zoning)<br />
• Head switching free ()<br />
• Requests issued one at a time<br />
- No caching in disks<br />
- Head must pass over sector after getting a read<br />
- By the time OS issues next request, too late for next sector<br />
• Slower CPUs, memory<br />
- Noticeable cost for block allocation algorithms
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