Lecture on Storage Devices

Hard Drives

• Definition: A hard drive consists of spinning magnetic platters.
• Non-volatile Storage: Retains data even when powered off.
• Random Access: Data can be accessed without sequentially forwarding or rewinding like tape drives.
• Components:
  • Platters: Spin at high speeds.
  • Actuator Arms: Move back and forth to find data.
  • Heads: Located at the arm's end, used for data retrieval and writing.
• Rotational Speeds:
  • Example: 5,400 RPM with latency ~5.5 ms.
  • Faster speeds like 15,000 RPM reduce latency to ~2 ms.
• Sizes:
  • 3.5 inch drives for desktops.
  • 2.5 inch drives common in laptops.

Solid State Drives (SSD)

• Non-volatile: No moving parts, less risk of mechanical failure.
• Performance: Faster than traditional hard drives.
• Interfaces:
  • SATA: Common for both HDD and SSD.
  • mSATA: Miniature form, used in mobile devices.
  • M.2: Smaller form factor, connects directly to PCIe bus.
• Advantages:
  • Smaller size allows for more compact devices.
  • Higher throughput with NVMe.

NVMe and M.2 Interfaces

• NVMe (Non-Volatile Memory Express): Designed for SSDs, offers lower latency, higher throughput.
• M.2 Form Factor:
  • Connects directly to the motherboard.
  • Supports PCIe for faster data transfer.
  • Different keys (B, M) need to be matched with the motherboard.

Flash Memory

• EEPROM: Electrically Erasable Programmable Read-Only Memory.
• Non-volatile: Retains data without power.
• Limitations:
  • Limited write cycles.
  • Not suitable for archival storage.
• Examples:
  • USB flash drives, SD cards, microSD cards, CompactFlash.

Optical Drives

• Use: Storage using a laser to read/write on optical disks.
• Types:
  • CD-ROM, DVD-ROM, Blu-ray.
• Applications: Archival media, non-rewritable storage.
• Availability: Internal and external options, becoming less common.