Computer Fundamentals: Storage

Storage

• Storage is a way to keep information long term.

Types of Storage

• Classified into three categories: Primary Storage, Secondary Storage, and Tertiary Storage.

Primary Storage

• Also known as main memory.
• Connected directly or indirectly to CPU through memory bus.
• Examples include RAM, ROM, and Cache.

Secondary Storage

• Not directly accessible by CPU.
• Computer uses its input/output channels to access secondary storage and transfers the desired data using intermediate area in primary storage.
• Examples include hard disks.

Hard Disk

• Main and usually largest data storage device in the computer.
• Can store anywhere from 160 GB to 2 TB.
• Hard disk speed is measured in rotations per minute (RPM), ranging from 4500 to 7200 RPM.
• Disk access time is measured in milliseconds.

Tertiary Storage

• Typically involves a robotic mechanism that mounts and dismounts removable mass storage media into a storage device.
• Comprehensive computer storage system that is usually very slow, used to archive data that is not accessed frequently.
• Primarily useful for extraordinary large data stores, accessed without human operators.

Offline Storage

• Also known as disconnected storage.
• Not under the control of a processing unit.
• Must be inserted or connected by a human operator.
• Examples include floppy disks, USB flash drives, and memory cards.

Methods of Storage

• Paper
• Optical
• Magnetic
• Solid State

Paper Storage

• Pros: no need for electricity or internet, confidential information can be easily locked away.
• Cons: can be hard to make backups, hard to convert or reuse, takes up lots of space.

Optical Storage

• Examples: CDs, DVDs, and Blu-Ray.
• Uses different reflections of light to read data, and a laser to write data.
• Pros: reliable, good portability, easy to pack and carry.
• Cons: per unit, have a smaller capacity than alternative, slower read/write speed, needs a disc drive to use.

Magnetic Storage

• Examples: hard disk drives (HDD), cassettes, and swipe cards.
• Data is written by changing magnetism on the disk/tape and read by detecting this.
• Pros: available with large capacities and cheap to buy, usually reliable, although failures do occur.
• Cons: generally not durable, slower read/write times compared to SSDs.

Solid State Drives

• Have no moving parts.
• Electronic circuits are used to store the data.
• Examples: SSDs, flash memory devices like USB memory sticks, and memory cards (like SD cards).
• Pros: generally reliable, can be very durable, can be portable, generally faster read/write times.
• Cons: higher cost per GB, sometimes have a limited number of writes leading to reliability problems long term.

Learn about the basics of computer storage, including primary, secondary, and tertiary storage, and how they are classified based on accessibility and data saving methods.