Understanding HDD Rotational Latency vs Seek Time
Short answer
C The process indicates Average latency time, which is the time spent waiting for the desired data block to rotate under the disk head after seeking the correct track.
Question
Key Takeaways
The key trap is confusing 'seek time' (head movement) with 'latency' (rotation). The prompt specifies the head is already at the track, isolating the rotational wait.
This question tests knowledge of hard disk drive performance metrics. The correct answer is C, identifying the waiting period for data rotation as average latency time.
Common mistake: Option B (Average seek time) is the most common mistake because candidates associate any head-related action with seeking. However, seek time ends once the head arrives; the subsequent wait is purely rotational.
Expert Analysis
The scenario describes the time interval during which the disk head is stationary at the correct track, waiting for the specific data sector to rotate into position under the read/write head. In hard disk drive (HDD) mechanics, this duration is known as rotational latency or simply latency.
Let's break down why the other options are incorrect based on standard storage performance metrics:
- Seek time refers to the time it takes for the actuator arm to move the disk head from its current position to the target track. The question explicitly states the head "moves to the track... and waits," implying the seek phase has already concluded or is distinct from the waiting phase.
- Average waiting time is a broader term often associated with queueing theory or I/O scheduling delays, not the physical mechanical delay of rotation.
- Moving time is not a standard technical term in this context; it likely conflates with seek time but lacks precision.
The comment provided mentions that average latency is calculated as half a rotation, which aligns with the definition of rotational latency. Since the head is already at the track, the only remaining mechanical delay is the rotation of the platter. Therefore, the process indicated is Average latency time.
Exam Strategy
When analyzing storage performance questions, isolate the physical actions described. If the head is moving, think 'seek'. If the head is stationary and the disk is spinning, think 'rotational latency'. Always check if the movement phase is complete before evaluating the wait phase.
Frequently Asked Questions
What is the difference between seek time and rotational latency?
How is average rotational latency calculated?
Community Votes
100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 1 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 1
-
10c5cfe 👍 1 Answered BAverage Latency is generally calculated as the time it takes for a half-rotation of the disk.
Reader comments & corrections
No reader corrections yet — spotted an error or have a note? Share it below.