A non-volatile memory that is used to permanently store data that can be retrieved later on a computer is call as hard disk drive (in short hard drive, HD, or HDD). It is a piece of hardware in the computer. It is a secondary storage device that includes one or more disks on which data is written using a magnetic head, encased in an air-tight casing. Internal hard disks reside in a drive bay or drive slot, connected to the motherboard using an Advanced Technology Attachment (ATA), Small Computer System Interface (SCSI) or Serial ATA (SATA) cable. The device is powered by a connection to the power supply unit (PSU).
To load files for the operating system, software programs, and save personal files of a user, all computers have a hard drive installed in them. A computer must have one hard drive installed to function. If a computer does not have a hard drive, it cannot work properly.
Sometimes users confuse between RAM and storage devices. So, it is important to understand that by hard disk, we mean permanent memory or storage device and saved filed will remain even if the power is turned on, whereas RAM is a temporary memory and contents will be lost on turning off the power.
Features of Hard Disk Drives:
Hard Disks are mass storage devices that store data permanently to be used by the computer devices. But they are not the active source of data for computers, when ever computer or other devices need that or file that is stored in hard drive, the data or file can be retrieved from the hard disk into the main memory so that it can be used. The major characteristics of hard disks largely tell us about its storage capacity, size or form factor, speed of data access, type of connection with the computer, task it performs etc.
One of the most important features of a hard disk is how much data it can store. Capacity is mainly the only distinguishing feature between the identical models. Storage space of hard drives has exponentially grown over the years from kilobytes to gigabytes and terabytes whereas price has drastically reduced. Flash drive based hard disks provide huge storage capacity than platter-based hard drives. Flash-based hard drives are costlier than conventional platter-based hard drives.
Hard drives are classified by data read and write speeds. Speed of mechanical hard drives depends on the number of rotations per second. But, this is a rough speed and it cannot always elaborate about overall performance of disk. The overall performance of data access from a hard disk depends on the storage method, type of connection and device bandwidth used. Solid-state drives, using flash memory mechanism, are capable of reading and writing data faster than mechanical platter- based hard drives. Additionally, hard drives have a performance restriction due to type of device connection. For example, a hard drive using SATA will transfer data at a maximum rate of 1.5 Gbps irrespective of the fact that the device is capable of accessing data at faster rate. So, connection type also plays an important role in performance of a hard disk.
Size of Hard Disk and connection type
Hard drives are also classified by size of the device or the amount of space the device takes up and the way it is connected to the computer. Physical size is also called the form factor of the device. Various connection standards are available like SATA, SCSI, SAS and PATA. Now if a computer uses SATA hard drives then it must support the SATA standard. If a computer does not support a particular standard then that particular feature or standard can be added to computers using expansion cards. Hard drives are also characterized by size measurements, such as 1.8, 2.5 and 3.5 inches. A larger size hard disk will not fit in a device that uses a smaller form factor slot.
Functions and uses of a Hard Drive
The main function of a hard disk is to store operating system, software and save the files and documents created by user. As we use computer, we create documents, files and other information which needs to be stored. So, we need some mass storage to saves these items, software and files that allow us to conveniently use, retrieve and interact with the same. Whenever we want to access a document or application on our computer, we need to access it from the attached hard drive. The retrieval process depends on the size of the file. Computer takes more time to retrieve large files from hard disk to main memory as compared to small size files.
Hard disks are the integral part of a computer. It is a mass storage device that permanently stores data and shouldn’t be confused with main memory RAM of a computer where data is lost on switching off the power. Various types of hard disk are available in market. All our software, operating system, files and documents are stored in hard drives. Can we think how will we safeguard our data if all the mass storage devices vanish out?