Computer Hardware Fundamentals - Hard Disks and Solid State Drives

Hard Disk

• A hard disk is a sealed case containing one or more circular platters or disks that store data, instructions, and information.

• It is used by the computer system for storing crucial and important data.

• It is non-volatile, meaning it can store data even if no power is supplied.

• Data or programs stored are preserved unless intentionally wiped out or overwritten.

Form Factors

• Form factors define the physical dimensions and specifications of hard drives, influencing their compatibility with different devices.

5 ¼” Form Factor

• Based on the original drive bay size.

• Now obsolete.

3 ½” Form Factor

• Introduced by Sony in 1991.

• Uses a reduced width and depth but with similar height as the half-height 5 ¼” form factor.

Advantages of using 3 ½” Form Factor

• Enhanced rigidity.

• Manufacturing ease.

• Increase in speed.

• Power conservation.

• Noise and heat reduction.

• Improved seek performance.

2 ½” Form Factor

• Introduced by Prairie Tek in 1988.

• Best suited for laptops and notebook PCs.

Common 2 ½” Form Factor Thickness:

• 8.5 mm

• 9.5 mm

• 12.5 mm

• 12.7 mm

• 17.0 mm

• 19.0 mm

Reasons why most manufacturers prefer thinner sizes:

• Size reduction.

• Power reduction.

• Enhanced rigidity.

1.8” Form Factor

• Introduced by Integral Peripherals in 1991.

• Mounts seamlessly in most PCMCIA (now called PC Card) slots.

• Ideal as detachable storage for laptops and notebook systems.

1” Form Factor

• Developed by IBM in 1988.

• Also called MicroDrive.

• Platter approximately the size of a quarter.

• Capable of storing 4 GB or more.

SATA and PATA

• PATA (Parallel Advanced Technology Attachment), also known as IDE (Integrated Drive Electronics), is an older interface used for connecting hard drives, CD/DVD drives, and other storage devices to a computer.

• PATA uses a parallel data transfer method, meaning data is transmitted in multiple bits at once, requiring wider ribbon cables and larger connectors.

• PATA has been largely replaced by SATA in modern computers.

• SATA (Serial Advanced Technology Attachment) is a newer interface developed as a replacement for PATA.

• SATA uses a serial data transfer method, meaning data is transmitted one bit at a time, allowing for faster data transfer speeds and thinner cables with smaller connectors.

• SATA is now the most common interface used for connecting hard drives, SSDs, and other storage devices to a computer.

SATA vs. PATA Comparison:

Components

Logic Boards

• Contains the electronic controller and bus adapter circuit.

• Includes data and power connectors.

• Features configuration jumpers/switches.

Hard Drive Interfaces

• Integrated Drive Electronics (IDE)

• Serial ATA (SATA)

• Small Computer System Interface (SCSI)

Integrated Drive Electronics (IDE)

• The controller is integrated into the disk drive.

• Also known as AT Attachment (ATA), Enhanced IDE (EIDE), or Parallel AT Attachment (PATA).

• Main hard drive uses the primary IDE cable, while the CD-ROM drive and others share the secondary IDE cable.

Serial ATA (SATA)

• Has several advantages over PATA, including superior cabling and connectors, higher bandwidth, and greater reliability.

• Although SATA and PATA are incompatible at the physical and electrical levels, adapters are readily available which allow SATA drives to be connected to PATA interfaces and vice versa.

Small Computer System Interface (SCSI)

• Standard for communication between a subsystem of peripheral devices and the system bus.

• Can contain and be used by up to 7 or 15 devices, depending on the SCSI standard.

• Provides better performance and greater expansion capabilities for many internal and external devices including hard drives, CD-ROM drives, DVD-ROM drives.

• Tends to be faster but more expensive and difficult to install than similar IDE 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 to the drive, 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 operation of a hard drive, the platters spin down, the cushion of air dissipates, and the heads drop back to the surface of the drive.

• Newer drives make use of an unload/load mechanism that does not allow the head to touch the surface of the platter even if it is powered off.

Tracks and Sectors

• Data is stored on hard drives in tracks (concentric rings) and sectors (pie-shaped wedges within each track).

Hard Disk Cylinders

• A cylinder is a set of tracks of the same diameter in a hard drive, spanning all platters.

Solid State Drives

• Solid State Drives (SSDs) are a type of storage device that uses NAND-based flash memory to store data.

• Unlike traditional hard disk drives (HDDs), which use spinning disks and read/write heads to access data, SSDs have no moving parts and store data electronically.

• This allows them to be much faster, more durable, and more reliable than HDDs.

Interfaces of SSDs:

• SATA

• mSATA

• M.2 SATA

• M.2 NVMe

SATA Solid State Drives

• SSDs that use the SATA interface.

mSATA Solid State Drives

• Mini-SATA SSDs, a smaller form factor for portable devices.

M.2 SATA Solid State Drives

• SSDs that use the M.2 form factor but communicate over the SATA interface.

M.2 Solid State Drives Sizes

• M.2 SSDs come in various sizes, such as 2242, 2260, 2280, etc., where the numbers represent the width and length in millimeters.

NVMe Solid State Drives

• NVMe stands for Non-Volatile Memory Express, which is a type of interface protocol designed to allow Solid State Drives (SSDs) to communicate with the rest of the computer system more efficiently than traditional storage interfaces such as SATA or SAS.

• NVMe is specifically optimized for SSDs that use NAND flash memory, which is the most common type of flash memory used in modern SSDs.

• NVMe SSDs are designed to take advantage of the fast access times and high transfer rates of NAND flash memory, and they use the PCIe (Peripheral Component Interconnect Express) interface to connect to the computer's motherboard.

• PCIe is a high-speed interface that is commonly used for graphics cards and other high-performance peripherals.

NVMe SSD PCIE Gen 3 vs. Gen 4

• NVMe Gen 3 was introduced in 2013 and is the third generation of the NVMe interface.

• It uses the PCIe 3.0 interface and provides up to 8 GT/s (gigatransfers per second) per lane, which allows for maximum theoretical bandwidth of up to $32 \text{ GB/s}$ (gigabytes per second) with 4 lanes.

• NVMe Gen 3 SSDs typically have a maximum read and write speed of around $3,500 \text{ MB/s}$, making them significantly faster than traditional SATA-based SSDs.

• NVMe Gen 4 was introduced in 2019 and is the fourth generation of the NVMe interface.

• It uses the PCIe 4.0 interface and provides up to 16 GT/s per lane, which allows for maximum theoretical bandwidth of up to $64 \text{ GB/s}$ with 4 lanes.

• NVMe Gen 4 SSDs typically have a maximum read and write speed of around $7,000 \text{ MB/s}$, which is more than twice as fast as NVMe Gen 3 SSDs.

• NVMe Gen 4 is also backward-compatible with PCIe 3.0, so NVMe Gen 4 SSDs can be used in systems that only support PCIe 3.0.