FCFS can cause the disk arm to travel long distances unnecessarily. We need a smarter approach that minimizes seek time.
SSTF (Shortest Seek Time First) always picks the request closest to the current disk head position, minimizing seek time.
- Keep track of current disk head position
- For each new request, calculate seek distance from current position
- Service the request with smallest seek distance
- Repeat until queue empty
- Reduces average seek time vs FCFS
- Can cause starvation for distant requests
- Greedy algorithm (local optimum, not global)
- Pros: faster than FCFS. Cons: may starve edge requests
- Built from: Disk Scheduling, FCFS
- Builds into: SCAN, C-SCAN
- Related: Disk Structure
- Contrasts with: FCFS (optimized vs simple)
- Starvation: requests at disk edges may never be served if center is busy
- Not optimal globally (greedy choice)
- Must recalculate distances after each service