Overview
This lecture covers the main types of storage devices—magnetic, optical, and solid state—describing their technologies, uses, advantages, disadvantages, and their evolving role in data storage.
Magnetic Media and Storage Devices
- Magnetic media stores data using magnetized areas representing binary values (1s and 0s).
- Examples include magnetic tape drives and hard disk drives (HDDs).
- Magnetic tape drives store data serially, making access slow but offering high capacity and low cost; used for backups and batch processing.
- HDDs use multiple magnetic platters and allow direct access to data; faster than tape drives but contain moving parts prone to damage.
- Portable hard drives resemble HDDs but are external, offering convenience for data transfer and backup, yet are also vulnerable to damage and loss.
Optical Media and Storage Devices
- Optical media uses laser technology to read/write data; common forms are CD, DVD, and Blu-ray discs.
- Three main types: R (Recordable—write once), RW (Rewritable—write multiple times), and ROM (Read-Only Memory—pre-recorded).
- CDs and DVDs use red laser and store data in spirals; DVDs may have double layers for higher capacity.
- Blu-ray discs use blue lasers for higher precision and larger capacity (up to 50GB double layer).
- Advantages: optical media is affordable and useful for music, films, and backups; Blu-ray offers high capacity and encryption.
- Disadvantages: limited rewriting for R-type discs, slower write speeds for RW types, compatibility issues, and Blu-ray discs are expensive.
Solid State Media and Storage Devices
- Solid state devices (SSDs, pen drives, memory cards) store data in memory cells using floating gate transistors.
- SSDs replace traditional HDDs in many devices, offering faster boot times and no moving parts.
- Pen drives (flash drives, memory sticks) are portable solid state devices used for file transfer and backups.
- Memory cards (SD, XD, CF cards) are small, removable, and commonly used in cameras and phones.
- Advantages: fast access, portable, durable, not affected by magnets, and easy data transfer.
- Disadvantages: limited write cycles, more expensive per GB than HDDs, can be lost easily, and may be less reliable over time.
The Future of Storage Devices
- CDs and DVDs are becoming obsolete in favor of flash-based devices and cloud streaming.
- Data is increasingly stored or accessed through SSDs, pen drives, and online/cloud services for convenience and accessibility.
Key Terms & Definitions
- Magnetic Media — storage devices that use magnetism to record data.
- Optical Media — devices using lasers to read/write data (e.g., CDs, DVDs, Blu-ray).
- Solid State Media — storage with no moving parts, using memory cells (e.g., SSDs, pen drives).
- Serial Access — data must be read in sequence (e.g., magnetic tapes).
- Direct Access — data can be read from any position (e.g., HDD, SSD).
- ROM (Read-Only Memory) — data can only be read, not written or erased.
- R (Recordable) — disc can be written once.
- RW (Rewritable) — disc can be erased and rewritten multiple times.
Action Items / Next Steps
- Review chapter 3 quiz to test understanding of storage device concepts.
- Compare advantages and disadvantages of each storage technology for potential exam questions.