Operating Systems - Disk Scheduling - SSTF, SCAN, C-SCAN
You are designing a disk scheduler for a real-time system where predictability and fairness are critical. Which algorithm would you choose and why?
You are designing a disk scheduler for a real-time system where predictability and fairness are critical. Which algorithm would you choose and why?
hard🌍 Real-world Scenario Q9 of Q15
Step-by-Step Solution
Solution:
Step 1: Identify real-time system requirements
Predictability and fairness are key, requiring bounded and uniform wait times.Step 2: Evaluate SSTF
SSTF minimizes seek time but can cause starvation and unpredictable delays.Step 3: Compare SCAN and C-SCAN
SCAN provides bounded wait but can favor requests near reversal points; C-SCAN offers uniform wait times by scanning circularly.Step 4: Consider FCFS
FCFS is fair but can have poor seek performance and unpredictable delays.Final Answer:
Option B -> Option BQuick Check:
C-SCAN balances fairness and predictability for real-time needs [OK]
Quick Trick: C-SCAN ensures uniform wait and fairness for real-time systems [OK]
Common Mistakes:
MISTAKES- Choosing SSTF for throughput over fairness
- Confusing SCAN's fairness with C-SCAN's uniformity
Trap Explanation:
PITFALL- Candidates often pick SSTF for speed, ignoring fairness and predictability needs.
Interviewer Note:
CONTEXT- Evaluates ability to select algorithms based on system requirements.
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