Hard Drives Information
Hard drives are integral non-volatile electronic data storage units inside computers. Traditionally hard-wired into the computer, they also include removeable hard disks or drives. Hard drives are also called hard disks, hard disk drives or fixed disk drives. Most computers have one hard drive located inside the computer case. If a computer has one hard drive, it is usually called drive C. If a computer has additional hard drives, they are called drives D, E, F, etc. The amount of information a hard drive can store is measured in bytes. Removable cartridges are hard disks encased in a metal or plastic cartridge, so they can be removed just like a floppy disk. Removable cartridges are very fast, though usually not as fast as fixed hard drives. Common types include the Iomega Jaz and Zip drives.
Important device specifications to consider when searching for hard drives includes capacity and transfer rate. Capacity is the amount of space available to store data. Transfer rate is the speed at which bits of data are sent. For example, this could describe the rate at which the bits of information are read from the disk and sent to the drive's controller (internal rate), or characterize data exchange between the controller and PC's CPU (external rate). The dimensions of length, width, and height are important to consider, especially for those hard drives that mount inside a rack or chassis.
Mounting options for hard drives include chassis mount, free standing, integrally mounted, panel mount, and rack mount. An important environmental parameter to consider when searching for hard drives is the operating temperature.
Common interface choices for hard drives includes:
Fibre channel is an interface that allows up to 2 Gigabit per second data transfer and maps several common transport protocols including IP and SCSI, allowing it to merge high-speed I/O and network functionality in a single connectivity technology.
The IEEE 1394 standard is a cross-platform implementation of the high-speed serial data bus that can move large amounts of data between computers and peripheral devices, like hard drives. It features simplified cabling, hot swapping, and transfer speeds of up to 400 megabits per second.
Integrated drive electronics (IDE) describes hard drive controller circuitry. These types of interfaces may also be referred to as ATA and UDMA. SCSI (Small Computer System Interface) is a parallel interface standard used by Apple Macintosh computers, PCs, and many UNIX systems for attaching peripheral devices to computers.
Universal serial bus is the standard serial bus for low-to-medium speed peripheral device connections to personal computers, including keyboards, mice, modems, printers, joysticks, audio functions, monitor controls, etc.
Hard drives must adhere to certain standards to have proper design and functionality. Example standards include ISO DIS 18943 (Care and handling of magnetic storage drives).
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