Comp111: Operating Systems
Classroom Exercise 16
Disks and Layers
Fall 2017

group member 1: ____________________________ login: ______________
group member 2: ____________________________ login: ______________
group member 3: ____________________________ login: ______________
group member 4: ____________________________ login: ______________
group member 5: ____________________________ login: ______________
group member 6: ____________________________ login: ______________
group member 7: ____________________________ login: ______________
group member 8: ____________________________ login: ______________

  1. Over time, disks naturally become "fragmented", in the sense that the blocks of a single file get spread out all over the disk. Why?

  2. A disk can be "defragmented" by ensuring that -- to the extent possible -- blocks from a single file are stored next to one another on the same track. Why is this advantageous?

  3. Is there any conceivable advantage for the filesystem driver to know the geometry of the disk (rather than just the number of blocks)? Why or why not?
  4. Physically, a disk is striped with alternating inode groups and block groups, rather than having one large section of inode groups and one large section of block groups. Why is this a good practice?

  5. The swap partition used for virtual memory is often not organized like a filesystem; in particular, it allocates each process memory segment as a contiguous set of blocks on the disk. Why is this a good practice? Why is it even possible?

  6. (Advanced) When a disk becomes severely corrupted, it is often possible to recover all the files, but without knowing their names. Why?

  7. (Advanced) The disk scheduler uses the concept of geometry in its scheduling, but the geometry is fake. How can the scheduler deal with the fact that the geometry of tracks -- as reported to it by the disk -- is only approximate?