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Storage management is a critical function of an operating system (OS) that involves the handling, organization, and maintenance of data storage resources. This module will cover the key concepts, structures, and techniques used in storage management.

Key Concepts in Storage Management

Storage Hierarchy:
- Primary Storage: Fast, volatile memory (e.g., RAM).
- Secondary Storage: Non-volatile storage (e.g., hard drives, SSDs).
- Tertiary Storage: Removable storage (e.g., tapes, optical disks).
- Quaternary Storage: Networked storage (e.g., cloud storage).
Storage Devices:
- Hard Disk Drives (HDDs): Magnetic storage with moving parts.
- Solid State Drives (SSDs): Flash memory with no moving parts.
- Optical Disks: CDs, DVDs, Blu-ray discs.
- Magnetic Tapes: Used for backups and archival storage.
File Systems:
- File Allocation Table (FAT): Simple, widely compatible file system.
- New Technology File System (NTFS): Advanced file system with security features.
- Extended File System (ext): Common in Linux environments.
Storage Management Techniques:
- Partitioning: Dividing a storage device into isolated sections.
- Formatting: Preparing a partition to hold data by setting up a file system.
- Mounting: Making a file system accessible at a certain point in the directory tree.

Storage Management Functions

Disk Scheduling

Disk scheduling algorithms determine the order in which disk I/O requests are processed. Common algorithms include:

First-Come, First-Served (FCFS): Processes requests in the order they arrive.
Shortest Seek Time First (SSTF): Selects the request with the shortest seek time.
SCAN (Elevator Algorithm): Moves the disk arm across the disk, servicing requests in one direction.
C-SCAN (Circular SCAN): Similar to SCAN but only services requests in one direction, then jumps back to the beginning.

Example: FCFS Disk Scheduling

def fcfs_disk_scheduling(requests, head_start):
    seek_sequence = []
    current_position = head_start
    total_seek_time = 0

    for request in requests:
        seek_sequence.append(request)
        total_seek_time += abs(current_position - request)
        current_position = request

    return seek_sequence, total_seek_time

# Example usage
requests = [98, 183, 37, 122, 14, 124, 65, 67]
head_start = 53
sequence, seek_time = fcfs_disk_scheduling(requests, head_start)
print("Seek Sequence:", sequence)
print("Total Seek Time:", seek_time)

RAID (Redundant Array of Independent Disks)

RAID is a technology that combines multiple disk drives into a single unit to improve performance and provide redundancy. Common RAID levels include:

RAID 0: Striping without redundancy.
RAID 1: Mirroring for redundancy.
RAID 5: Striping with parity for fault tolerance.
RAID 6: Similar to RAID 5 but with extra parity for additional fault tolerance.

Storage Virtualization

Storage virtualization abstracts physical storage resources to create a single, unified storage pool. This allows for more flexible and efficient storage management.

Practical Exercises

Exercise 1: Implementing SSTF Disk Scheduling

Implement the Shortest Seek Time First (SSTF) disk scheduling algorithm.

Solution

def sstf_disk_scheduling(requests, head_start):
    seek_sequence = []
    current_position = head_start
    total_seek_time = 0
    requests = sorted(requests)

    while requests:
        closest_request = min(requests, key=lambda x: abs(x - current_position))
        seek_sequence.append(closest_request)
        total_seek_time += abs(current_position - closest_request)
        current_position = closest_request
        requests.remove(closest_request)

    return seek_sequence, total_seek_time

# Example usage
requests = [98, 183, 37, 122, 14, 124, 65, 67]
head_start = 53
sequence, seek_time = sstf_disk_scheduling(requests, head_start)
print("Seek Sequence:", sequence)
print("Total Seek Time:", seek_time)

Exercise 2: Understanding RAID Levels

Research and compare the different RAID levels (0, 1, 5, 6) in terms of performance, redundancy, and use cases. Create a table summarizing your findings.

Solution

RAID Level	Description	Performance	Redundancy	Use Cases
RAID 0	Striping without redundancy	High	None	High-performance applications
RAID 1	Mirroring	Moderate	High	Critical data storage
RAID 5	Striping with parity	High	Moderate	General-purpose storage
RAID 6	Striping with double parity	Moderate	High	High-availability storage solutions

Conclusion

In this module, we covered the fundamental concepts of storage management, including storage hierarchy, storage devices, file systems, and storage management techniques. We also explored disk scheduling algorithms and RAID levels, providing practical examples and exercises to reinforce the concepts. Understanding these principles is crucial for efficient and effective storage management in operating systems.

Storage Management

Key Concepts in Storage Management

Storage Management Functions

Disk Scheduling

Example: FCFS Disk Scheduling

RAID (Redundant Array of Independent Disks)

Storage Virtualization

Practical Exercises

Exercise 1: Implementing SSTF Disk Scheduling

Solution

Exercise 2: Understanding RAID Levels

Solution

Conclusion

Fundamentals of Operating Systems

Module 1: Introduction to Operating Systems

Module 2: Resource Management

Module 3: Concurrency

Module 4: File Structures