Operating System
OS Part-1
OS Part-2
- File Concepts and Access methods
- Free Space Management and Allocation methods
- Directory Systems and Protection
- File Organization, Sharing and Implementation issues
- Disk and Drum Scheduling
- I/O Devices Organisation & I/O Buffering
- I/O Hardware, Kernel I/O subsystem and Transforming I/O Requests to Hardware Operations
- Device Drivers and Path Management
- Device Driver Sub Modules and Procedure
- Device Scheduler and Handler
- Interrupt Service Routine (ISR)
- File System in Linux and Windows
OS Part-3
- Process and Process Control Block(PCB)
- Process Scheduling( Preemptive and Non Preemptive)
- Scheduling Algorithms
- Algorithm Evaluation
- Multiple Processor Scheduling
- Real Time Scheduling
- Operations on Processes
- Threads
- Inter-Process Communication
- Precedence Graphs
- Critical Section Problem
- Semaphores
- Classical Problems of Synchronization
- DeadLock
- Deadlock Prevention and Avoidance
- Deadlock Detection and Recovery
- Process Management in Linux
OS Part-4
- Memory Hierarchy in OS
- Concepts of Memory Management
- MFT and MVT
- Logical and Physical Address Space
- Swapping
- Contiguous and Non Contiguous Memory Allocation
- Paging
- Segmentation
- Paging Combined with Segmentation
- Structure and Implementation of Page Table
- Virtual Memory in OS
- Cache Memory Organization
- Demand Paging
- Page Replacement Algorithms
- Allocation of Frames and Thrashing
- Demand Segmentation
OS Part-5
- Distributed Operating System: Introduction and Types
- Distributed OS: Design Issues
- Distributed OS: File System
- Distributed OS: Remote File Access
- Remote Procedure Call(RPC)
- Remote Method Invocation(RMI)
- Distributed Shared Memory
- Parallel Processing and Concurrent Programming
- Security and Threats Protection in Distributed OS
- Security Design Principles and Authentication in Distributed OS
- Sensor Network and Parallel OS
Disk & Drum Scheduling in Operating System
1. Disk & Drum Scheduling Kya Hota Hai?
Operating System (OS) me disk scheduling aur drum scheduling techniques ka use kiya jata hai taaki storage devices (HDD, SSD, ya drum memory) efficiently kaam karein. Iska main goal hai:
Seek time kam karna Disk access fast banana System performance improve karna
2. Disk Scheduling in OS
Disk Scheduling Kya Hota Hai?
Disk scheduling ka matlab hai read/write requests ko aise manage karna ki access time minimum ho.
Important Disk Parameters
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Seek Time – Read/write head ko requested track tak pahunchne ka time.
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Rotational Latency – Disk ko rotate hone ka time taaki sector head ke niche aa jaye.
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Transfer Time – Data ko read/write hone ka actual time.
3. Disk Scheduling Algorithms
1. First-Come, First-Served (FCFS)
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Kaise kaam karta hai? Jo request pehle aati hai, usko pehle process kiya jata hai.
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Example:
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Request queue: 98, 183, 37, 122, 14, 124, 65, 67
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Agar head 53 par hai, toh ye sequence follow hoga:
53 → 98 → 183 → 37 → 122 → 14 → 124 → 65 → 67
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Fayda: Simple aur fair hai.
Nuksan: Seek time zyada ho sakta hai.
2. Shortest Seek Time First (SSTF)
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Kaise kaam karta hai? Jo request head ke sabse kareeb hoti hai, usko pehle process kiya jata hai.
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Example:
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Head 53 par hai, aur requests hain: 98, 183, 37, 122, 14, 124, 65, 67
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Sabse nearest 37 hai, toh 37 → 14 → 65 → 67 → 98 → 122 → 124 → 183
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Fayda: Fast hai, seek time kam hota hai. Nuksan: Starvation ho sakta hai (kuch requests delay ho sakti hain).
3. SCAN (Elevator Algorithm)
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Kaise kaam karta hai? Disk head ek direction me move karta hai, sabhi requests complete karta hai, phir reverse karta hai.
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Example:
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Head 53 par hai aur right me move kar raha hai:
53 → 65 → 67 → 98 → 122 → 124 → 183, phir wapis left aayega.
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Fayda: Starvation problem solve karta hai. Nuksan: End requests ke liye delay ho sakta hai.
4. C-SCAN (Circular SCAN)
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Kaise kaam karta hai? SCAN ki tarah hai, lekin head reverse nahi karta, seedha last track se first track par jump karta hai.
Fayda: Requests ko uniform wait time milta hai. Nuksan: Kuch extra movement ho sakti hai.
5. LOOK & C-LOOK
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LOOK: SCAN ki tarah, lekin last request ke baad reverse hota hai.
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C-LOOK: C-SCAN ki tarah, lekin last request tak jaake first request par jump hota hai.
Fayda: Unnecessary head movement kam hoti hai. Nuksan: Extreme requests delay ho sakti hain.
4. Drum Scheduling in OS
Drum Scheduling Kya Hota Hai?
Drum scheduling old computer systems me use hota tha jisme drum memory ek rotating storage device hoti thi.
Drum Scheduling Features
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-> Fixed rotation speed hoti thi.
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-> Data sequentially read hota tha (random access nahi hota tha).
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-> Cyclic Scheduling hoti thi – Rotation ke saath data synchronize hota tha taaki fast access ho.
5. Disk Scheduling vs. Drum Scheduling
| Feature | Disk Scheduling | Drum Scheduling |
|---|---|---|
| Storage Type | Hard Disk, SSD | Magnetic Drum |
| Read/Write Head | Move hota hai | Fixed hota hai |
| Performance Focus | Seek time kam karna | Rotation sync rakhna |
| Modern Use | Abhi bhi use hota hai | Ab obsolete hai |
6. Conclusion
Disk scheduling ka use fast data access aur seek time kam karne ke liye hota hai. Drum scheduling sirf purane systems me use hoti thi. Modern OS me efficient disk scheduling performance improve karta hai.