# hpca/sample-final/samplefinal2/problem6

Problem 6. 15 Points - Storage

A 12,000RPM disk drive has 2 platters, with 100,000 tracks per surface, 1,000 sectors

per tracks, and 512 data bytes per sector. Each sector also has a 128-bit error detection

code that can detect all errors in its sector but cannot correct any errors. The head takes

ten microseconds (a 100,000th

cylinder, and multi-cylinder movements are done at the same speed (100,000 cylinders

per second). The disk controller is very fast (assume zero latency for everything it does)

and the I/O bus has very large (assume infinite) bandwidth.

A) [2 point] How many heads does the disk drive have?

B) [3 points] Assuming that the disk controller and the drive itself are not servicing

any other requests, what is the worst-case time needed to read a sector from the

disk?

of a second) to move from one cylinder to an adjacent

C) [3 points] If we use two of these disk drives in a RAID0 configuration, and if the

array is full (it contains as much data as its capacity allows), what is the best-case

time needed to read all of the data stored in the array?

D) [3 points] If we use five of these disk drives in a RAID5 configuration, and if the

array is full (it contains as much data as its capacity allows), what is the best-case

time needed to read all of the data stored in the array?

E) [4 points] If we use three of these disk drives in a RAID5 configuration and we

are extremely lucky, what is the maximum number of sectors that can be damaged

in this array that still allow us to recover all of the data?