Deep Trend Analysis: The Exam Blueprint for Module 6

An analysis of 13 exam questions spanning from 2019 to 2024 reveals a highly predictable pattern for Module 6.

Topic Weightage Distribution

The 3 Key Exam Patterns

1. The Guaranteed Numerical (7-14 Marks) — Disk Scheduling Every single year features a disk scheduling numerical. You will be given:

• A request queue (cylinder numbers)
• A current head position
• Sometimes a previous request (to determine direction for SCAN/C-SCAN)

You must calculate total head movement (in cylinders) for one or more algorithms. The most common algorithms tested: SSTF (2019, 2022, 2024), SCAN (2023), C-SCAN (2023), FCFS (2023).

2. The Definition Short Questions (2 Marks) These test your ability to recall acronyms and precise terminology:

• SPOOLING = Simultaneous Peripheral Operation Online [2023 Q1c]
• RAID = Redundant Array of Independent Disks [2024 Q1c]
• Seek time = time to move the disk arm to the desired track [2022 Q1h]
• Free-space management technique = Bit Vector [2024 Q1i]
• Bad blocks can cause = Data loss or corruption [2024 Q1f]

3. The Conceptual Comparison (7 Marks) Questions asking you to compare two concepts appear regularly:

• Linked vs Indexed allocation [2024 Q9a]
• CAV vs CLV (Constant Angular Velocity vs Constant Linear Velocity) [2023 Q8a]
• Short notes on I-Node [2023 Q9b]

High-Yield Subjective Bank

Ensure you have a 200-300 word written response prepared for each of these recurring questions:

1. [2019 Q9, 7 marks] Explain the SSTF disk scheduling algorithm. Why does SSTF scheduling tend to favor middle cylinders over the innermost and outermost cylinders?

   • Hint: Discuss statistical bias — the head spends more time near the middle because there are cylinders on both sides providing nearby requests. Edge cylinders only have requests on one side, so the head rarely travels to the edge. This creates starvation for edge-cylinder requests.

2. [2024 Q9a, 7 marks] Compare and contrast linked and indexed disk allocation strategies.

   • Hint: Discuss direct access speed (indexed is fast, linked is slow for random access), external fragmentation (neither has it), space overhead (pointers in each block vs index block), file growth, reliability (FAT chain break vs inode corruption). Use the comparison table from Section 2.

3. [2023 Q8a, 5 marks] Differentiate between Constant Linear Velocity (CLV) and Constant Angular Velocity (CAV).

   • Hint: CAV = constant RPM, higher transfer rate on outer tracks, used by HDDs. CLV = variable RPM, constant transfer rate, used by optical drives. Discuss sector density and complexity.

4. [2023 Q9b, 7 marks] Write short notes on I-Node.

   • Hint: Define inode as the UNIX data structure storing file metadata. List fields (file size, permissions, timestamps, block pointers). Explain the 12 direct + 1 single indirect + 1 double indirect + 1 triple indirect pointer structure. Provide the maximum file size calculation (4 TB + 4 GB + 4 MB + 48 KB for 4 KB blocks, 4-byte pointers).

5. [2022 Q2a, 7 marks] Describe seek time, rotational latency, and random-access time and their relationship in context of magnetic disks. Draw the moving-head mechanism.

   • Hint: Total access time = Seek Time + Rotational Latency + Transfer Time. Seek is the head movement to the correct cylinder. Rotational latency is waiting for the sector to rotate under the head (average = half a rotation). Transfer time is the actual data read/write. Illustrate with a diagram showing the disk arm, platters, tracks, and sectors.

PYQ Numerical Summary Table

All the disk scheduling numericals from the PYQ set are solved in detail in Section 3. Here is a quick-reference summary:

To view complete PYQ, go here: https://pyqdeck.in/it/it_sem5/it_sem5_106503/practice/chapter/