Practice Problems

Assume a disk with the following characteristics: Number of sectors per track $=20$

Number of tracks per surface $=50$

Number of surfaces $=2($called a double$-$sided disk$)$ Number of characters per sector $=1,024$

Arm movement time $=0\mathrm{.}4$ msec to move $1$ track in any direction Rotation speed $=2,400$ rev$/$min

$1.$ How many characters can be stored on this disk?

$2.$ What are the best$-$case, worst$-$case, and average$-$case access times for this disk? $($Assume that the average seek operation must move $20$ tracks.$)$

$3.$ What would be the average$-$case access time if we could increase the rotation speed from $2,400$ rev$/$min to $7,200$ rev$/$min$?$

$4.$ What would be the average$-$case access time of the disk of the previous problem if we could reduce the arm movement time to $0\mathrm{.}2$ msec to move $1$ track in any direction? $($Again$,$ assume that the average seek operation must move $20$ tracks.$)$

$5.$ Defragmenting a disk means to reorganize files on the disk so that as many pieces of the file as possible are stored in sectors on the same track, regardless of the surface it is on$.$ Explain why defragmentation can be beneficial.