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CHAPTER 4: SECONDARY STORAGE (optical disc (commonly store items in a…
CHAPTER 4: SECONDARY STORAGE
storage: holds data, instructions and information for future use
storage medium
the physical material on which a computer keeps data, instructions, and information
storage device
the computer hardware that records and/or retrieves items to and from storage media
reading: transferring items from a storage medium into memory
writting: transferring items from memory into storage medium
secondary storage
1)Provides permanent or nonvolatile storage.
2)Items on a storage medium remain intact even when you turn off a computer or mobile device
important characteristic for secondary storage
capacity- how much a particular storage medium can hold
storage devices- hardware that reads data & programs from storage media
media- physical material that holds data & programs
access speed- measures amount of time required by the storage to retrieve data & programs
hard disk
stores and organizes files using tracks, sectors and cylinders.
sensitive instruments.
use rigid metallic platters that are stacked one on top of another
The clearance between a hard disk read/write head and the platter is about 0.000001 inch thick.
contains one or more inflexible, circular platters that use magnetic particles to store data, instructions and information
A head crash occurs when a read/write head touches the surface of a platter – resulting in a loss of data or sometimes loss of the entire disk
types
internal hard disk
external hard disk
solid-state storage: Data and information are stored and retrieved electronically. Contain no moving parts
memory cards
Widely used in laptops, smartphones, GPS navigation systems
USB flash drives
Capacity of 1 GB to 256 GB
Portable
Connect to USB port
solid-state drive
Faster and more durable than hard disks
Access to slash memory or solid state storage
optical disc
commonly store items in a single track that spirals from the center of the disc to the edge
A CD-ROM can be read from but not written to
consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser
A CD-R is an optical disc on which users can write once, but not erase
A CD-RW is an erasable multisession disc
DVD-RW, DVD+RW, and DVD+RAM are high-capacity rewritable DVD formats
A DVD-ROM is a high-capacity optical disc on which users can read but not write on or erase
A DVD-R or DVD+R are competing DVD-recordable WORM formats, on which users can write once but not erase
cloud storage: an Internet service that provides storage to computer or mobile device users
advantage
Allow others to access their files
View time-critical data and images immediately
Store large files instantaneously
Store offsite backups
Access files from any computer
Provide data center functions
disadvantage
Access Speed
File security
store companies
google
microsoft
dropbox
amazon
apple
enterprise storage
TAPE:a magnetically coated ribbon of plastic capable of storing large amounts of data and information
SAN: a high-speed network with the sole purpose of providing storage to other attached servers
NAS: a server that is placed on a network with the sole purpose of providing storage to users, computers, and devices attached to the network
RAID: duplicates data, instructions, and information to improve data reliability
mass storage devices
Enterprise storage system
Safe use of data across an organizational network
Devices include:
Networked attached storage (NAS)
RAID systems
Organizational cloud storage
File servers
To meet the needs of organizations requiring large amounts of secondary storage requirements