Overview
This lecture explains different types of computer storage devices, highlighting their structure, operation, advantages, and limitations, including hard drives, solid state drives (SSDs), and flash and optical memory.
Hard Drives (HDDs)
- Hard drives use spinning magnetic platters to store data non-volatilely, so data remains when power is off.
- Data on hard drives is accessed randomly, not sequentially like a tape drive.
- Inside, actuator arms move across platters to read or write data, which creates mechanical speed limits and potential failures.
- Platters spin at speeds like 5400 or 15000 RPM; higher RPM means lower latency and faster access.
- Multiple platters and heads allow data reading/writing on both surfaces of each platter.
- Common HDD sizes: 3.5-inch for desktops and 2.5-inch for laptops.
Solid State Drives (SSDs) and Interfaces
- SSDs store data with non-volatile memory and have no moving parts, reducing mechanical failure risk.
- SSD performance is much higher than HDDs due to direct data access and no spin latency.
- SATA (Serial ATA) is a common storage interface but can be a bottleneck for fast SSDs.
- mSATA (mini-SATA) offers a compact interface for SSDs, mainly for mobile devices, but is now largely replaced.
- M.2 is a smaller interface for SSDs, supporting higher transfer speeds, especially when using NVMe.
- NVMe (Non-Volatile Memory Express) uses the PCIe bus for much faster SSD throughput (up to 4 GB/s).
- M.2 SSDs can have different "keys" (B, M, or both); motherboard compatibility must be checked before installation.
Flash Memory
- Flash memory (EEPROM) is non-volatile and used in USB drives, SD cards, and microSD cards.
- Flash drives have write cycle limits, which can prevent further writing after many uses.
- Flash storage is not recommended for long-term archiving due to risk of data loss or damage.
- Types include USB flash drives, SD/microSD cards, and legacy formats like CompactFlash.
Optical Drives
- Optical drives use lasers to read/write data from disks (CD-ROM, DVD-ROM, Blu-ray).
- Often utilized for archival storage on media that is not meant to be changed.
- Available as internal or external devices via USB.
Key Terms & Definitions
- Non-volatile — Storage that retains data without power.
- Random Access — Ability to retrieve data from any location directly.
- Rotational Latency — Delay waiting for disk platter to rotate to the data location.
- SATA (Serial ATA) — Common interface for hard drives and some SSDs.
- AHCI (Advanced Host Controller Interface) — Protocol for moving data via SATA.
- NVMe (Non-Volatile Memory Express) — High-speed protocol for SSDs using PCIe.
- M.2 — Compact storage interface supporting both SATA and NVMe SSDs.
- EEPROM — Electrically Erasable Programmable Read-Only Memory, used in flash drives.
Action Items / Next Steps
- Review motherboard documentation to determine compatible SSD interface and key type.
- Backup data stored on flash drives and avoid using them for long-term storage.
- Read about interface protocols (AHCI vs NVMe) for further understanding.