Magnetic Disk Drives
HARD DRIVES (HARD DISK DRIVE, HDD)
Hard disk drives are so named because they contain hard magnetic disks inside the housing. They are designed to store large quantities of information, and they don’t need to be continuously powered in order to hold that data. The vast majority of PCs used today have at least one hard drive, and in almost all of these, the hard drive is used to store the OS, programs, and data. When a computer boots, depending on BIOS settings, the computer searches for boot files on different disk drives, most commonly the floppy drive first, then the hard drive, and then a CD drive.
Basic Hard Drive Characteristics
Externally, hard drives have a power connector, a data connector, and jumpers. We discuss jumpers later in this chapter. The power connector is connected to one of the drive connectors from the power supply, and the data connector is connected to the appropriate drive connector on the motherboard. Internally, hard drives have spinning magnetic platters and heads. Heads are small devices that store and pick up magnetic information from the platters; they have similarities to heads on cassette tape machines. Storage areas on the platters are divided into portions called cylinders, sectors, and clusters. Information about these parameters appears in the hard drive documentation and often on the paper label on the housing.Under the Type category, there are usually three or more settings: User, None, and Auto (other settings might not apply to stationary hard drives). The None setting disables the drive. User allows the user to input the settings manually. If you choose User, the settings must match those of the drive exactly. Auto has the computer detect the drive information; on the vast majority of newer computers, Auto is the best setting.