Operating Systems - Disk Scheduling - SSTF, SCAN, C-SCAN
If a disk scheduler using SSTF is modified to include aging (increasing priority of waiting requests over time), what is the expected impact on starvation and average seek time?
If a disk scheduler using SSTF is modified to include aging (increasing priority of waiting requests over time), what is the expected impact on starvation and average seek time?
hard🎤 Interviewer Follow-up Q10 of Q15
Step-by-Step Solution
Solution:
Step 1: Understand aging in SSTF
Aging increases priority of waiting requests, preventing indefinite postponement (starvation).Step 2: Analyze impact on seek time
Servicing older, possibly distant requests earlier increases average seek time compared to pure SSTF.Step 3: Conclude trade-off
Eliminating starvation comes at the cost of increased average seek time.Final Answer:
Option C -> Option CQuick Check:
Aging trades off starvation for higher average seek time [OK]
Quick Trick: Aging prevents starvation but may increase seek time [OK]
Common Mistakes:
MISTAKES- Assuming aging has no effect
- Believing aging reduces seek time
Trap Explanation:
PITFALL- Candidates overlook trade-offs, expecting aging to improve all metrics.
Interviewer Note:
CONTEXT- Tests understanding of trade-offs in algorithm modifications.
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