Secondary Storage Notes

Secondary Storage

Storage

  • Holds data, instructions, and information for future use.

  • Reading: transferring items from storage to memory.

  • Writing: transferring items from memory to storage.

Important Characteristics of Secondary Storage

  • Media: Physical material that holds data & programs.

  • Capacity: Number of bytes a storage medium can hold.

  • Storage devices: Hardware that reads data & programs from storage media.

  • Access speed: Time required to retrieve data & programs.

Hard Disk

  • Contains inflexible, circular platters using magnetic particles.

  • Uses rigid metallic platters stacked on top of each other.

  • Stores and organizes files using tracks, sectors, and cylinders.

  • Sensitive instruments; head crash occurs when read/write head touches the platter, resulting in data loss.

Two Basic Types of Hard Disk

  • Internal Hard Disk: Fast access, located inside the system unit, cannot be easily removed.

  • External Hard Disk: Slower access, connected via USB or Thunderbolt, easily removed.

Hard Disk Performance Enhancement Techniques

  • Disk Caching: Uses cache to anticipate data needs, utilizing fast RAM memory for quick retrieval.

  • RAID (Redundant Array of Independent Disks): Combines multiple physical hard drives into a single logical unit to improve performance.

  • File Compression: Reduces file size.

  • File Decompression: Expands compressed files.

Solid State Storage

  • Contains no moving parts; data stored and retrieved electronically.

  • Types: Solid-state drives, Memory cards, USB flash drives

Flash Memory Storage

*Solid-state drive
* Faster access times
* Faster transfer rates

*Memory card
* Removable flash memory device.
* Common types include CF, SDHC, SDXC, miniSD, microSD, microSDHC, microSDXC, xD Picture Card, Memory Stick PRO Duo, and M2.

*USB Flash Drives
* Plugs into a USB port.

Cloud Storage

  • Internet service providing storage to computer or mobile device users.

  • Supplied by servers that provide cloud or online storage.

Advantages:

  • Access files from any computer.

  • Store large files instantaneously.

  • Allow others to access files.

  • View time-critical data and images immediately.

  • Store offsite backups.

  • Provide data center functions.

Disadvantages:

  • Access Speed.

  • File Security.

Optical Discs

  • Flat, round, portable disc made of metal, plastic, and lacquer; read and written by a laser.

  • Uses reflected light to represent data: lands (1s and 0s) and pits (bumpy areas).

  • Uses tracks and sectors to organize and store files with a single spiral track.

  • CD-ROM: Read-only, single-session disc.

  • CD-R: Write once.

  • CD-RW: Erasable multisession disc.

  • DVD-ROM: High-capacity, read-only.

  • DVD-R/DVD+R: Write once.

  • DVD-RW/DVD+RW/DVD+RAM: High-capacity rewritable formats.

  • CD: Ideal for music and light data storage.

  • DVD: Better suited for video and moderate data storage.

  • Blu-ray: Designed for high-definition video and large data storage.

Mass Storage Devices

  • For organizations needing large amounts of secondary storage.

  • Enterprise storage system: safe use of data across an organizational network.

  • Devices include file servers, networked attached storage (NAS), RAID systems, organizational cloud storage.

Enterprise Storage

  • Hardware for managing and storing data with high efficiency and availability.

  • Network attached storage (NAS): a server to provide storage to users, computers, and devices attached to the network

  • Storage area network (SAN): high-speed network dedicated to providing storage to other attached servers.

  • RAID (Redundant Array of Independent Disks): duplicates data to improve reliability.

  • Tape: magnetically coated ribbon for storing large amounts of data; read and written by a tape drive.

Other Types of Storage

  • Magnetic stripe card: Contains a magnetic stripe for storing information.

  • Smart card: Stores data on an integrated circuit.

  • RFID tag: Antenna and memory chip that transmits information via radio waves.

  • Microfilm and microfiche: Store microscopic images on film.