Hard disks the most common

Operating System Fundamentals
78 The File Manager The File Manager is the part of the operating system that is responsible for the management of long-term storage devices such as hard disks. The File Manager provides a framework (or a
hierarchical structure) for the organization of data that is stored on a disk. The primary responsibilities of the File Manager include The organization of similar data (text, images, music and sounds, video, etc) in some manner, and putting that data into files. The organization of files into directories and folders. The organization of different levels of folders. The management of different partitions in a disk. The management of multiple disks for data storage. The File Manager has additional responsibilities that are based on the primary responsibilities listed above. These include Partitioning and formatting disks. Establishing file-naming rules or conventions. Providing data integrity. Providing error recovery and prevention tools. Providing file security. Providing directory paths. Providing command sets to manipulate files. Data Storage Strategies Data storage strategies refer to how the operating system physically organizes and stores pieces of files on a disk. There are three common data storage strategies
1. Contiguous Allocation Strategy
2. Linked Allocation Strategy
3. Indexed Allocation Strategy
Contiguous Allocation Strategy
The contiguous allocation strategy is perhaps the simplest strategy for an operating system to setup. Ina contiguous allocation file system, all pieces of a file are stored in contiguous (or physically adjacent) storage spaces on a disk. To keep track of files stored on the disk, the operating system maintains a file directory that lists the names of the files, the start block for the file on the disk, and the actual size of the file. The contiguous strategy has both advantages and disadvantages. Advantages of the Contiguous Allocation Strategy Easy to setup. Easy approach for the sequential access of data. Disadvantages of the Contiguous Allocation Strategy

Operating System Fundamentals
79 Not easy to expand the size of a file. Difficult to manage file fragmentation. OS must allocate and reserve contiguous space during the initial creation of the file. Figure 6.1 (below) shows the allocation of disk space for files, and a file directory, fora sample hard disk.

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