Data Storage Peripherals: Magnetic, Optical, and Flash Systems

Magnetic Storage Peripherals

Magnetic storage uses a ferromagnetic layer material (disks or hard drives).

Floppy Disk Drives

Floppy disks read and record information. Key parts include:

• Engine torque mechanism
• Shaft reading heads
• Ejecting mechanism and floppy connector

Hard Disk Drives (HDDs)

HDDs use tough aluminum platters that spin at high speed. The drive writes or reads data tracks.

Methods for Storing Information

• CHS (Cylinder, Head, Sector): Information is located by knowing the face, track, and sector.
• LBA (Logical Block Addressing): Data is accessed by calling a logical block number and searching for it.

HDD Physical Structure

The physical structure consists of:

• Platters (disks)
• Heads
• Spindle motor (engine torque)
• Head displacement mechanism (DLS heads)
• Electronic control buffer
• Power connector

HDD Interfaces

• IDE (Integrated Drive Electronics): Uses UDMA-66 or higher transfer methods, typically requiring an 80-wire ribbon cable.
• SATA (Serial ATA): Offers improved data transfer rates. Cables can be up to 1 meter long. Supports hot-swapping and provides better performance.
• SCSI (Small Computer System Interface): Physically similar to IDE connectors, but not identical. Primarily used in servers due to higher transfer rates and reliability.

Hard Drive Characteristics

Key characteristics of hard drives include:

• Access time
• Seek time
• Latency
• Rotational speed (RPM)
• Transfer rate
• Buffer interface size
• Transfer mode

External Drives

External drives can be used with laptops or PCs. They often require partitioning management, similar to internal drives.

Optical Storage Media

Optical storage refers to digital storage technologies.

CD Technology and Components

Key elements of a CD drive include:

• Reading head
• Disc holder/monitor
• Rotation motor (up to 12x speed)
• Disk loading mechanism
• DAC (Digital-to-Analog Converter): Sends a signal to play audio through speakers.
• Front buttons and eject hole

Rotation Methods

• CLV (Constant Linear Velocity): Used by many readers; speed varies depending on track position.
• CAV (Constant Angular Velocity): The disc always turns at the same speed, resulting in higher speeds toward the outer edge.

CD-ROM Specifications

CD technology was developed around 1979 (audio) and 1980 (standard). Data storage was standardized in 1984, allowing up to 600MB of data.

Transfer Speed

The minimum transfer speed for audio reading is 150 KB/s (1x speed).

DVD Drives

DVDs universally use the UDF (Universal Disk Format). They are sensitive; protective coatings are thin, and they are affected by temperature (maximum recommended 23°C).

Blu-ray Discs (BD)

Blu-ray is designed for high-definition video. Single-layer discs store 25GB, and multi-layer discs can store up to 100GB (up to 4 layers).

Blu-ray Advantages Over DVD

Blu-ray offers:

• Stable, high-precision writing.
• Anti-scratch protective layer.
• Protective layer resistant to light, improving writing reliability.
• Higher precision without losing quality.
• Incorporates copy protection programs.

Both DVD and Blu-ray typically use UDF and ISO 9660 file systems.

Other Storage Technologies

Flash Memory

Flash memory is a type of non-volatile memory that can be accessed rapidly.

USB Flash Drives

USB drives are light and small devices, historically ranging from 64MB up to 32GB.

Memory Cards

Flash memory encased in a protective housing, typically featuring four contacts. Examples include PC Cards (for laptops), CompactFlash I/II, SD, miniSD, microSD, and xD.

Legacy Magnetic Storage

Magneto-Optical Disks (9cm)

These 9cm diameter disks primarily stored data, though some could be used for music. Maximum capacity was typically 840MB.

Zip Disks

Zip disks offered transfer rates of 1 MB/s, using IDE/ATA/SCSI interfaces. Capacities ranged from 100MB, later increasing to 250MB and 750MB.

Jaz Disks

The successor to the Zip disk, Jaz offered 1GB or 2GB capacity. Both Zip and Jaz technologies are now obsolete, replaced by CDs and DVDs.

Super Disks (LS-120/LS-240)

These drives featured reduced head size and were compatible with standard floppy disks. Housing units offered 120MB and 240MB capacities, using ATAPI, SCSI, USB, or parallel port interfaces.

Magnetic Tapes

Magnetic tapes are primarily used for creating security backups of large amounts of data.