Capacity Planning of Computer Systems and Networks, Operation Management

Problem:- 1
A system containing one CPU and a disk is serving database transactions. A transaction gets service from CPU and then from the main memory before leaving this system. In case, the access to the main memory is a miss, the transaction moves to receive service from a disk. In case of a miss, the CPU needs to process the transaction again. (We are assuming simple system here, real systems are complex).
CPU processing time for each visit by a transaction = 0.03 sec
Disk access time = 0.02 sec
No. of disk access generated by each transaction visit to disk mean that after each access it goes back to CPU)
Memory access time = 0.001 sec
Miss from the main memory = 10 %
= 10 (note this doesn’t
Transaction range = 10-50 transactions/sec (Check for 10,20...50)
Part 1:- Calculate the service demand and the utilization of all the resources. Determine which resource is the bottleneck for the system with throughput bounds analysis to show the feasibility of the system for the given range of transactions.
(5 marks) Part 2:- The system is not feasible for the complete range of the transactions. Following
three upgrades can be applied to the system:
a) Add two more CPUs, each CPU gets 1/3rd of the transactions
b) Double the main memory size, (half the number of misses).
c) Double the number of disks, each disk gets half of the transactions
d) Replace the disk with a faster disk of access time 0.015 sec.
Calculate the utilization of each resource and their throughput for the following combinations of upgrades, also point out which device is the bottleneck in each case (if any). Consider the transaction rate as 50/sec
1) a
2) a + b
3) a+ b + c
4) a+ b + d
(8 Marks)
CS9334 Assignment 1, March 28, 2013, 4:03 PM, Page 1
Part-3 (Bonus Marks) :- Another transaction type is to be introduced to the system that takes 5 disk accesses and CPU processing time of 0.1 sec. The combined transaction rate is 50 transactions/sec. With the modified system of the part2 (Option - 3) ( with upgrades of a+b+c), calculate the highest number of new transactions that the system can support. What is the impact of introducing this new transaction type?
(5 Marks)
Problem 2:-
Two sets of analysts working on a marine project require access to a database server. Set A and B include 4 and 5 analysts respectively. Set A analyst queries require 10 records to be read from the DB server’s disk on average, and require CPU processing time of 20 msec. Set B analyst queries require 5 records to be read from the DB server’s disk on average, and CPU time of 70 msec. The disk read time per record is 10msec. If only one set of analysts is allowed to access the DB server at any time, calculate the throughput of the DB system for both set of analysts.
(12 Marks)
Note: Numbers without explanation will receive poor marks.

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