Chapter 37, homework/file-disks:

  sector label is in the middle of the sector:

       0           1	   ...
 |<--------->|<--------->| ...

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Chapter 38:

raid 0

  disk = addr % N

  offset = addr / N

  addr = offset * N + disk

raid 1

  disk1 = (addr % (N/2)) * 2

  disk2 = disk1 + 1

  offset = addr / (N/2)  (if odd choose odd-numbered disk, else choose even-numbered disk)

  addr = offset * (N/2) + disk / 2

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raid 4

  P0 = B0 XOR B1 XOR B2 XOR B3

  P1 = B4 XOR B5 XOR B6 XOR B7

If B6 is lost it can be recovered from B4 XOR B5 XOR P1 XOR B7:

  ( P1 = B4 XOR B5 XOR B6 XOR B7 ) XOR P1 XOR B6

    B6 = B4 XOR B5 XOR P1 XOR B7

Note that anything XOR'd with itself is 0: Y XOR Y = 0