Hard Drive Architecture and Storage Fundamentals

Hard Drive Fundamentals

A hard drive is a non-volatile storage device that uses magnetic properties. Each side of the disk contains small areas that can be magnetized as positive (1) or negative (0), allowing for the storage of large amounts of digital data.

Disk Geometry

Disk geometry refers to the total number of cylinders, sides, and sectors per track.

Logical Structure

The Master Boot Record (MBR) is the first sector of the hard drive. It saves the partition table and contains the Master Boot code, which reads the partition table and transfers control to the active partition to initiate the system boot process.

• Partitioned space: Disk space allocated to a specific partition.
• Non-partitioned space: Disk space not assigned to any partition.

HDD Features

• Capacity: The total amount of information that can be stored.
• Transfer methods:
  • PIO: Micro-intermediary between RAM and the hard drive (5.6 MB/s – 16.6 MB/s).
  • DMA: Transfer system between the hard drive and RAM (16.6 MB/s – 133 MB/s).
• Access time: Time taken for read/write operations.
• Rotational speed: Measured in RPM.
• Latency: Delay in data retrieval.
• Cache: Stores read/write data to improve efficiency.
• Other factors: Interface, physical size, noise, and temperature.

IDE Connection Mechanisms

The IDE (Integrated Drive Electronics) connection uses a 40-pin flat cable to connect to the motherboard. Historically, systems featured two IDE ports, though modern systems typically have one or none.

Jumpers

Jumpers are small connectors located at the rear of the disk used for configuration:

• Stand Alone / Master: Single drive configuration.
• Master-Slave: Used for non-ATA configurations.
• Slave: Secondary drive configuration.
• Cable Select: Automatic configuration via cable.

SATA (Serial ATA)

SATA was developed to resolve IDE limitations. SATA jumpers regulate disk speed (e.g., SATA3 to SATA2) rather than drive hierarchy. Connections utilize 7-pin and 15-pin cables.

Data Transmission

• Serial transmission: Bits are transmitted one by one on a single line; used for long distances.
• Parallel transmission: Bits are transmitted in groups across several lines simultaneously; used within the computer.

Storage Device Comparison

Storage devices vary by registration, volatility, speed, and capacity, ranging from processor cache and RAM to hard drives.

Physical Structure of the HDD

• Platter: Magnetic-sensitive elements constructed of resistant materials.
• Tracks: Concentric rings extending from the outside to the center.
• Cylinder: A set of tracks aligned vertically.
• Sectors: Subdivisions of tracks.
• Face: A side of the disk.
• Engines: Components that move the plates and read/write heads.

LBA and Partitioning

LBA (Logical Block Addressing) is the transfer mode between drives and their drivers. Regarding disk organization:

• Primary partitions: The main divisions of the disk. A drive can have up to 4 primary partitions, or 3 primary and 1 extended partition.
• Extended partition: Acts as a container for countless logical drives.