Disk Scheduling.

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As we know, a process needs two type of time, CPU time and IO time. For I/O, it requests the Operating system to access the disk.

       However, the operating system must be fare enough to satisfy each request and at the same time, operating system must maintain the efficiency and speed of process execution.

The technique that operating system uses to determine the request which is to be satisfied next is called disk scheduling.

Let's discuss some important terms related to disk scheduling.

Seek Time

Seek time is the time taken in locating the disk arm to a specified track where the read/write request will be satisfied.

Rotational Latency

It is the time taken by the desired sector to rotate itself to the position from where it can access the R/W heads.

Transfer Time

It is the time taken to transfer the data.

Disk Access Time

Disk access time is given as,

Disk Access Time = Rotational Latency + Seek Time + Transfer Time

Disk Response Time

It is the average of time spent by each request waiting for the IO operation.

Purpose of Disk Scheduling

The main purpose of disk scheduling algorithm is to select a disk request from the queue of IO requests and decide the schedule when this request will be processed.

Goal of Disk Scheduling Algorithm

• Fairness
• High throughout
• Minimal traveling head time

Disk Scheduling Algorithms :

The list of various disks scheduling algorithm is given below. Each algorithm is carrying some advantages and disadvantages. The limitation of each algorithm leads to the evolution of a new algorithm.

• FCFS scheduling algorithm
• SSTF (shortest seek time first) algorithm
• SCAN scheduling
• C-SCAN scheduling
• LOOK Scheduling
• C-LOOK scheduling

    NEXT :

• FCFS scheduling algorithm

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1. What is an Operating System ?
2. Discuss the structure off OS ?
3. Explain type of OS?
4. Explain Function of OS?
5. Explain OS Services ?
6. What do mean by system call ?List different type ofsystem call available ?

1. what is process ? and Characteristics ?
2. What is different process state? explain the same in details?
3. write short note on user level and kernal level threads?
4. explain what is thread and its type ?
5. explain scheduler ? (short term,medium term,and long term)
6. state and explain scheduling criteria ?
7. Explain scheduling algorithm ? [ FCFS,SJF,PRIORITY,ROUND ROBINE.]    

1. What is process synchronization ? explain critical section problem and race condition ?
2. what is Race Condition ?
3. what is critical section problem?
4. explain classical problem of synchronization?
5. explain bounded - buffer problem?
6. explain reader - writer problem ?
7. explain Dining Philosophers Problem ?
8. explain semaphores ? its type ?

1.  What is deadlock ?
2. What are the 4 condition to produce deadlock ?
3. explain methods of handling deadlock ?
4. explain in detail deadlock prevention ?
5. write short note on deadlock avoidance ?
6. explain deadlock detection ? 
7. explain Banker algorithm with example ? 

1. What are memory management ?
2. what is contiguous memory allocation and non - contiguous memory allocation ?
3. explain concept of paging with neat diagram?
4. differentiate contiguous and non - contiguous memory allocation ?
5. explain in details various partitioning memory management?
6. explain the concept of Segmentation ?
7. what is Thrashing explain in details ?

1. explain virtual memory concept in details ? with advantages and disadvantages ?
2. explain page replacement algorithm ?
3. explain LRU , Optimal ,FIFO.