GATE CS 2015 Set 1 Q48 — I/O Scheduling

To find the total time needed to read the entire file, we need to calculate the time required to access a single sector and then multiply it by the total number of sectors ($2000$).

For each sector access, the total time consists of three components:

Step 1: Calculate the Rotational Time

The disk rotates at $10000$ RPM (rotations per minute).

Time for one complete rotation ($T_{\text{rev}}$):

Step 2: Calculate the Average Rotational Latency

The average rotational latency ($T_{\text{rotational}}$) is half of the time for one complete rotation:

Step 3: Calculate the Sector Transfer Time

Since there are $600$ sectors per track, the time to read one sector ($T_{\text{transfer}}$) is the time for one full rotation divided by the number of sectors per track:

Step 4: Calculate the Total Time for One Sector

Given that the seek time ($T_{\text{seek}}$) is $4$ ms:

Step 5: Calculate the Total Time for the Entire File

The file contains $2000$ sectors, and every sector access requires a seek:

Thus, the total time needed to read the entire file is 14020 milliseconds.