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Solutions for Third Quiz

Solutions for Third Quiz. COSC 6360 Fall 2014. First question. Which Kerberos entities share these secrets? (4 points per correct line). Answer. Which Kerberos entities share these secrets? (4 points per correct line). Answer.

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Solutions for Third Quiz

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  1. Solutions forThird Quiz COSC 6360 Fall 2014

  2. First question • Which Kerberos entities share these secrets? (4 points per correct line)

  3. Answer • Which Kerberos entities share these secrets? (4 points per correct line)

  4. Answer • Which Kerberos entities share these secrets? (4 points per correct line)

  5. Answer • Which Kerberos entities share these secrets? (4 points per correct line)

  6. Answer • Which Kerberos entities share these secrets? (4 points per correct line)

  7. Answer • Which Kerberos entities share these secrets? (4 points per correct line)

  8. Second question • What is the main feature of SHA hash algorithms? (10 points)

  9. Answer • What is the main feature of SHA hash algorithms? (10 points) • Any change to the hashed data will (with very high probability) change the hash value • Can be used to verify the integrity of data

  10. Third question • Consider a RAID level 6 array with ten disks. Against which potential failures—or combinations of failures—does the array protects its data? (2×10 points)

  11. Answer • Consider a RAID level 6 array with ten disks. Against which potential failures—or combinations of failures—does the array protects its data? (2×10 points) • The simultaneous failure of two disks • The failure of one disk and several irrecoverable read errors on the other disks

  12. Fourth question • What is the cost of a write in a log-structured file system, when its segment cleaner has to clean four segments to produce two clean segments? (10 points)

  13. Fourth question • What is the cost of a write in a log-structured file system, when its segment cleaner has to clean four segments to produce two clean segments? (10 points)

  14. Answer • What is the cost of a write in a log-structured file system, when its segment cleaner has to clean four segments to produce two clean segments? (10 points) • The segment utilization is 2/4 = 0.5 • The cost of a write is 2/0.5 = 4 I/O ops

  15. Fifth question • According to Shah and Pâris, what is the relationship between the transmission delay of their protocol and the size of its sliding window? (10 points)

  16. Answer • According to Shah and Pâris, what is the relationship between the transmission delay of their protocol and the size of its sliding window? (10 points) • They are equal.

  17. Sixth question • What are the main advantages and disadvantages of using the asynchronous log updates in journaling file systems?(210 points)

  18. Answer • What are the main advantages and disadvantages of using the asynchronous log updates in journaling file systems?(210 points) • Main advantage:it is much fasterthan using synchronous log updates • Main disadvantage:it does not guarantee the durability of metadata updates

  19. Seventh question • Which dependency information do soft updates maintain? (10 points)

  20. Answer • Which dependency information do soft updates maintain? (10 points) • It keeps track of which i-node blocks must be updated before/after a given directory entry

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