An operating system controls all aspects of the computing environment. It works between the application and physical components of the computer system. One of the services it provides to the application is data access. The operating system also monitors and responds to user actions and the environment. It organizes and controls hardware components and manages the allocation of hardware resources. It provides basic security for the access and usage of all managed resources. An operating system also performs basic storage management tasks while managing other underlying components, such as the file system, volume manager, and device drivers.

1. Device Driver

A device driver is special software that permits the operating system to interact with a specific device, such as a printer, a mouse, or a hard drive. A device driver enables the operating system to recognize the device and to use a standard inter-face (provided as an application programming interface, or API) to access and control devices.

Disk partitioning was introduced to improve the flexibility and utilization ofHDDs. In partitioning, an HDD is divided into logical containers called logicalvolumes (LVs). For example, a large physical drive can be partitioned into multiple LVs to maintain data according to the file system’s and applications’ requirements. The partitions are created from groups of contiguous cylinders when the hard disk is initially set up on the host. The host’s file system accesses the partitions without any knowledge of partitioning and the physical structure of the disk. Concatenation is the process of grouping several smaller physical drives andpresenting them to the host as one logical drive.

The evolution of Logical Volume Managers (LVMs) enabled the dynamic extension of file system capacity and efficient storage management. LVM is software that runs on the host computer and manages the logical and physical storage. LVM is an optional, intermediate layer between the file system and the physical disk .The LVM provides optimized storage access and simplifies storage resource management. It hides details about the physical disk and the location of data on the disk; and it enables administrators to change the storage allocation without changing the hardware, even when the application is running.The basic LVM components are the physical volumes, volume groups, and logical volumes. In LVM terminology, each physical disk connected to the host system is a physical volume (PV).

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1. File System

• A file is a collection of related records or data stored as a unit with a name. A file system is a hierarchical structure of files. File systems enable easy access to data files residing within a disk drive, a disk partition, or a logical volume. A file system needs host-based logical structures and software routines that control access to files. It provides users with the functionality to create, modify, delete, and access files. Access to the files on the disks is controlled by the permissions given to the file by the owner, which are also maintained by the file system.

• A file system organizes data in a structured hierarchical manner via the use of directories, which are containers for storing pointers to multiple files. All file systems maintain a pointer map to the directories, subdirectories, and files that are part of the file system. Some of the common file systems are as follows:

  i.FAT 32 (File Allocation Table) for Microsoft Windows

  ii.NT File System (NTFS) for Microsoft Windows

  iii.UNIX File System (UFS) for UNIX

  iv.Extended File System (EXT2/3) for Linux

1. Application

• An application is a computer program that provides the logic for computing operations. It provides an interface between the user and the host and among multiple hosts. Conventional business applications using databases have a three-tiered architecture the application user interface forms the front-end tier; the computing logic forms, or the application itself is, the middle tier; and the underlying databases that organize the data form the back-end tier. The application sends requests to the underlying operating system to perform read/ write operations on the storage devices. Applications can be layered on the database, which in turn uses the OS services to perform R/W operations to storage devices. These R/W operations enable transactions between the front-end and back-end tiers.