Contiguous allocation

Contiguous allocation is the allocation scheme that works best for a file system implemented on a device that can only be accessed sequentially, such as a tape drive. In this allocation scheme, files are stored on the storage medium in contiguous blocks or sections.

Advantages of Contiguous Allocation:

1. Sequential Access: Since the device can only be accessed sequentially, contiguous allocation allows for efficient sequential access of files. When a file is accessed, the next block of the file is located in the adjacent physical location on the tape, which reduces the seek time and improves performance.

2. Simplified Addressing: With contiguous allocation, the starting address of a file and its size are sufficient to locate and access the entire file. This simplifies the addressing mechanism, as the file can be located by knowing only its starting address.

3. Reduced Fragmentation: Contiguous allocation minimizes external fragmentation, as files are stored in contiguous blocks. There is no need to search for free blocks or maintain a free space list, which reduces the overhead of file allocation.

4. Efficient Disk Utilization: Since files are stored contiguously, the storage space can be utilized more efficiently. There is no wasted space between files, resulting in higher overall disk utilization.

5. Simplicity: Contiguous allocation is a simple and straightforward allocation scheme, making it easier to implement and manage. It requires less complex data structures and algorithms compared to other allocation schemes.

Disadvantages of Contiguous Allocation:

1. Fragmentation: Contiguous allocation can lead to internal fragmentation when the allocated blocks are larger than the size of the file. This can result in wasted space within the allocated blocks.

2. Limited Flexibility: Contiguous allocation does not provide much flexibility in dynamically allocating and deallocating files. It may require large contiguous free space to allocate a file, which can be a challenge in situations where the available free space is scattered.

Overall, contiguous allocation is the most suitable allocation scheme for a file system implemented on a device that can only be accessed sequentially, such as a tape drive. It provides efficient sequential access, simplified addressing, reduced fragmentation, efficient disk utilization, and simplicity in implementation.