Midterm Exam - Stanford Secure Computer Systems Group
Midterm Exam - Stanford Secure Computer Systems Group Midterm Exam - Stanford Secure Computer Systems Group
– p. 6/16 Fast file system • New block size must be at least 4K - To avoid wasting space, use “fragments” for ends of files • Cylinder groups spread inodes around disk • Bitmaps replace free list • FS reserves space to improve allocation - Tunable parameter, default 10% - Only superuser can use space when over 90% full
– p. 7/16 FFS superblock • Contains file system parameters - Disk characteristics, block size, CG info - Information necessary to get inode given i-number • Replicated once per cylinder group - At shifting offsets, so as to span multiple platters - Contains magic to find replicas if 1st superblock dies • Contains non-replicated “summary info” - # blocks, fragments, inodes, directories in FS - Flag stating if FS was cleanly unmounted
- Page 1 and 2: - p. 1/16 Midterm Exam • Reminder
- Page 3 and 4: - p. 3/16 Original Unix file system
- Page 5: - p. 5/16 Problems with original FS
- 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. 6/16<br />
Fast file system<br />
• New block size must be at least 4K<br />
- To avoid wasting space, use “fragments” for ends of files<br />
• Cylinder groups spread inodes around disk<br />
• Bitmaps replace free list<br />
• FS reserves space to improve allocation<br />
- Tunable parameter, default 10%<br />
- Only superuser can use space when over 90% full
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