Storage Devices

Optical Storage

  • Overview of Optical Storage

    • Optical storage uses discs with microscopic bumps read by a laser beam.

    • CD-ROM (Compact Disc ROM)

      • First type of optical format for personal computers.

      • Capacity: Approximately 700 megabytes.

    • DVD-ROM (Digital Versatile Disc)

      • Upgrade to CD-ROMs.

      • Capacity: 4.7 gigabytes for single layer, 8.5 gigabytes for dual layer.

    • Blu-ray Disc

      • Newest optical format.

      • Capacity: 25 gigabytes for single layer, 50 gigabytes for dual layer.

    • Capable of both reading and writing information.

Writing Information to Optical Media

  • Writing does not create bumps but darkens areas with photosensitive dye.

  • Different formats of writing to optical media:

    • CD-RW (Compact Disc Rewriteable)

    • DVD-R/RW (DVD Read and Rewriteable)

    • DVD-R DL (Dual Layer DVD)

    • BDR (Blu-ray Disc Recordable)

    • BD-RE (Blu-ray Disc Recordable Erasable)

Solid-State Drives (SSD)

  • Overview of SSDs

    • No moving parts and non-volatile memory.

    • Quick access to information without delays common in spinning hard drives.

    • Commonly used interfaces:

      • PCI Express

      • 2.5-inch SATA SSD

      • M.2 Interface

        • Smaller size similar to memory modules.

        • Fast access speeds without SATA cables.

        • Direct access to PCI Express bus enhances throughput.

    • Key types for M.2 drives:

      • B key: Connects using two PCIe lanes.

      • M key: Connects with four PCIe lanes for maximum performance.

Hard Disk Drives (HDD)

  • Overview of HDD

    • Spinning magnetic storage drives with rapidly rotating platters.

    • Features moving parts including a spinning platter and actuator arm.

    • Access Speed:

      • Influenced by rotational speed; faster drives reduce latency.

      • Example: 5,400 RPM has 5.55 ms latency; 15,000 RPM provides shorter latency.

    • Disadvantages include mechanical failures due to moving parts.

Hybrid Drives

  • Solid State Hybrid Drives (SSHD)

    • Combine spinning drive with SSD memory.

    • SSD serves as a cache for faster access while the HDD stores data.

    • Same form factor as traditional hard drives.

Flash Drives

  • Overview of Flash Drives

    • Technically EEPROM (Electrically Erasable Programmable Read-Only Memory).

    • Non-volatile, retains data without power.

    • Limited number of writes, not ideal for archival storage.

  • Varieties of Flash Memory

    • USB Flash Drive: Standard portable storage.

    • Compact Flash: Older format for cameras.

    • SD (Secure Digital): Common in various devices, including smaller versions (mini SD, micro SD).

    • XD Picture Card: Used in some digital cameras.