A1.1.8 — Secondary Storage
Overview
Secondary memory is non-volatile storage that is not directly accessible by the CPU. Used for long-term data persistence. Also called external memory, auxiliary storage, or mass storage.
Storage Types
| Type | Technology | Advantages | Disadvantages |
|---|---|---|---|
| HDD (Hard Disk Drive) | Spinning magnetic platters. Read/write head moves across the surface. | High capacity, cheap per GB, reliable for long-term storage. | Slow, mechanical, can be noisy, vulnerable to physical damage. |
| SSD (Solid State Drive) | NAND flash memory. No moving parts. | Much faster than HDD, silent, durable, lower power consumption. | More expensive per GB, limited write cycles. |
| eMMC (Embedded Multimedia Card) | NAND flash soldered directly onto the motherboard. | Compact, low cost, good for portable devices. | Slower than SSD, not removable or upgradeable. |
| Optical Drive | Laser reads pits and lands encoded on a spinning disc. | Large capacity discs, good for archiving, compatible with older devices. | Fragile, slow data access, largely replaced by SSDs and cloud. |
| Flash Drive | NAND flash memory with a USB connector. | Portable, affordable, plug-and-play. | Easy to lose, lower capacity than HDD/SSD, data loss risk if damaged. |
| Memory Card | NAND flash in a small removable card format. | Portable, compact, used in cameras and phones. | Easy to lose, small capacity, not always compatible across devices. |
| NAS (Network Attached Storage) | One or more HDDs/SSDs connected to a network router. | Centralised shared storage for multiple users, scalable, can use RAID for redundancy. | Requires network setup and configuration, depends on network connection. |
Ninja Note: Know the difference between internal (HDD, SSD, eMMC) and external (flash drives, memory cards, external HDDs, NAS) storage. Also know that optical drives read pits and lands using a laser — that specific detail comes up in exams.