computer science assignment

   1. a) (24) The figures below represent a RAID 3 and a RAID 5 system each containing 5 disks and each employing. Assume that the RAID 3 system uses a bit-interleave factor such that complete blocks (i.e. strips) are written at one time to each disk. The parity information is used only to recover data in the event of a single disk failure (but not to verify data integrity).




Indicate whether each of the 6 transactions listed below would be possible for only the RAID 3 described above, for the RAID5 only, for both or for neither.

   1. Read strip 19 and read strip 20 at the same time
   2. Write strip 7 and read strip 9 at the same time
   3. Read strips 12 through 15 at the same time
   4. Write strip 20 and write strip 19 at the same time
   5. Write strip 2 and write strip 23 at the same time
   6. Write strip 9 and write strip 23 at the same time



b) (16) Assume that within the RAID 5 system the disk containing strip 22 fails and is no longer useable. Explain how strip 23 could still be properly updated. That is, explain the following:

    * What is the MINIMUM number of strips that would have to be read to generate the new parity block?
    * Which strips would have to be read?
    * Which strips would have to be written?
    * Of the reads and/or writes that would be performed, which ones could occur in parallel (i.e. at the same time)?



2.  (15) a) Write down a sequence of MIPS instructions that might be used as part of the exception handler that would determine whether an I/O interrupt has occurred.
(15) b) Is the exception handler executed by the CPU or by the system coprocessor (CP0)?

3. (15) Suppose that you were considering replacing your single-processor core system with a more powerful multi-core system. A certain program (10% of which is sequential and 90% of which is parallel) is executed on both the old and the new systems. An operating system capable of scheduling threads or tasks to available processors is used on both systems. If the only difference between the two systems is the number of processor cores, how many processor cores would the new system require to achieve a speedup factor of 4 for the program?

4.(15) Seventy-two percent of the code in a certain program can be executed in parallel and the remainder must be executed sequentially. If this program is executed on a symmetric multiprocessor (SMP) computer system that contains 8 processors each of which is rated at 148 MIPS when executing as a uniprocessor, what would be the effective MIPS rating for the SMP system when it is executing this single program? Keep Amdahl’s Law in mind while deriving your answer.