SAM Module 2

Device

DVD drive, flash memory card reader, etc.

Medium

Is inserted into the device to be used

Storage Devices

Are typically identified by a letter, can be internal, external, or remote, are nonvolatile

Logical File Representation

The user’s view of the way data is stored

Physical File Representation

The actual physical way the data is stored on the storage media as viewed by the computer

File

Anything stored on a storage medium, such as a program, document, digital image, or song

Filename

Name given to a file by the user

Folder

Name place on a storage medium into which files can be stored

Hard Drive

Used to store most programs and data

Magnetic Hard Drives

Use metal hard disks. Read/write heads magnetize particles to represent the data’s 0s and 1s

Solid-state Drives (SSD)

Use flash memory technology, use less power and have no moving parts, particularly appropriate for portable computers

Disk Access Time

Total time that it takes for a hard drive to read or write data. Consists of seek time, rotational delay, and data movement time

Disk Cache

Dedicated part of RAM used to store additional data adjacent to data retrieved during a disk fetch to improve system performance

Hybrid Hard Drive

Combination of flash memory and magnetic hard drive. Uses flash memory for cache. Allows encryption to be built into the drive

Partitions

Logically divides the physical capacity of a single drive into separate areas

File System

Determines the cluster size, maximum drive size, and maximum file size. FAT, FAT32, and NTFS

Optical Discs

Store data optically (using laser beams). Divided into sectors like magnetic discs but use a single spiral track. Data is stored in 0s and 1s

Pits and Lands

Are used to represent 1s and 0s, the transition between a pit and land represents a 1; no transition represents a 0

Read-only

Surface is molded or stamped to represent the data

Recordable or Rewritable

Reflectivity of the surface is changed by a laser

Optical Drives

Designed for the type of disc: CD, DVD, or Blu-Ray Disc (BD). Can be read-only, recordable, or rewritable. Downward compatible. Can support single or dual-layer discs

Burning

Recording data onto a disc

CD Discs

Use infrared lasers; hold 650 MB

DVD Discs

Use red lasers; hold 4.7 GB (single-layer)

BD Discs

Use blue-violet lasers; hold 25 GB (single-layer)

Read-only Discs

Can be read from, but not written to, by the user

Recordable Disc

Can be written to, but cannot be erased and reused

Rewrtitable Disc

Can be recorded on, erased, and overwritten just like magnetic discs

Chip-based Storage Medium

No moving parts so more resistant to shock and vibration, require less power, make no sound. Solid-state storage system

Flash Memory Card

A small card containing one or more flash memory chips, controller chips, and metal contacts to connect the card to the device or reader

USB Flash Drives

Consist of flash memory media and a reader in a single self-contained unit

Remote Storage

Using a storage device not directly a part of the computer being used

Network Storage

Via a local network

Network Attached Storage (NAS)

Connected directly to a network

Storage Area Network (SAN)

Separate network of hard drives or other storage devices which is attached to the main network

Smart Card

Credit card-sized piece of plastic that contains some computer circuitry (processor, memory, and storage)

Holographic Storage

Store data as holograms. An emerging type of 3D storage technology. Uses two blue laser beams to store data in three dimensions

Storage Server

Hardware device containing multiple high-speed hard drives

RAID (Redundant Arrays of Independent Discs)

Method of storing data on two or more hard drives that work together to do the job of a larger drive

RAID 0

Disk striping (spread files over two or more hard drives)

RAID 1

Disk mirroring (duplicate copy). Other level use a combination of striping and mirroring

Magnetic Tape

Plastic tape with a magnetizable surface that stores data as a series of magnetic spots