Computer Hardware: Hard Disk Fundamentals

Hard Disk

• A sealed case containing one or more circular platters or disks that store data, instructions, and information used by the computer system.
• Non-volatile in nature, allowing data to be stored even without power supply, and preserving data unless intentionally wiped out or overwritten.

Form Factors

• 5 ¼” Form Factor: based on original drive bay size, now obsolete.
• 3 ½” Form Factor: introduced by Sony in 1991, with enhanced rigidity, manufacturing ease, increased speed, power conservation, noise and heat reduction, and improved seek performance.
• 2 ½” Form Factor: introduced by Prairie Tek in 1988, best suited for laptop and notebook PCs, with common thicknesses of 8.5 mm, 9.5 mm, 12.5 mm, 12.7 mm, 17.0 mm, and 19.0 mm.
• 1.8” Form Factor: introduced by Integral Peripherals in 1991, mounts seamlessly in most PCMCIA slots, ideal for detachable storage in laptops and notebooks.
• 1” Form Factor: developed by IBM in 1988, also called MicroDrive, with a platter size similar to a quarter, capable of storing 4 GB or more.

SATA and PATA

• PATA (Parallel Advanced Technology Attachment): an older interface, using parallel data transfer, with wider ribbon cables and larger connectors, largely replaced by SATA.
• SATA (Serial Advanced Technology Attachment): a newer interface, using serial data transfer, with faster data transfer speeds, thinner cables, and smaller connectors, now the most common interface for hard drives and SSDs.
• SATA offers faster data transfer speeds (up to 6 Gbps), longer cable lengths (up to 1 meter), and lower power consumption, while PATA is slower (maximum 133 Mbps), with limited cable length (45 cm or less), and higher power consumption.

Components

• Logic Boards: contain electronic controllers, bus adapters, data and power connectors, configuration, and jumpers/switches.

Hard Drive Interfaces

• Integrated Drive Electronics (IDE): the controller is integrated into the disk drive, using AT Attachment (ATA) Enhanced IDE (EIDE) and Parallel AT Attachment (PATA).
• Serial ATA (SATA): has several advantages over PATA, including superior cabling and connectors, higher bandwidth, and greater reliability.
• Small Computer System Interface (SCSI): a standard for communication between peripherals and the system bus, providing better performance and expansion capabilities for internal and external devices.

Operation

• HDDs are composed of rotating disks or platters with heads that read and write data in circular rings.
• Read and write heads do not make contact with the media.
• When power is applied, the platters spin up to speed, and the buildup of air under the heads causes them to lift off the data surfaces.
• During power off, the platters spin down, the cushion of air dissipates, and the heads drop back to the surface of the drive.

Solid State Drives (SSDs)

• Use NAND-based flash memory to store data.
• Unlike traditional hard disk drives, SSDs have no moving parts and store data electronically, making them faster, more durable, and more reliable.
• Interfaces of SSDs: SATA, mSATA, M.2 SATA, M.2 NVMe.

NVMe Solid State Drives

• NVMe (Non-Volatile Memory Express) is a type of interface protocol designed for SSDs to communicate with the computer system efficiently.
• Optimized for SSDs using NAND flash memory, using the PCIe interface to connect to the motherboard.
• NVMe SSDs are designed to take advantage of the fast access times and high transfer rates of NAND flash memory.