Secondary storage permanently saves information for future use; to share information with others; to modify at later date Secondary storage is nonvolatile – stores programs and data as opposed to temporary storage (RAM) Characteristics include: Media or medium – actual physical materials that holds the data and programs Capacity – measures how much a particular storage medium can hold Storage devices – hardware that reads data and programs from storage media (most also write to storage media) Access speed or access time – measures the amount of time required by the storage device to retrieve data and programs Writing– process of saving information to the secondary storage device Reading – process of accessing information from secondary storage
Optical disks – large storage capacity (Key Term) Hard disk – large storage capacity and fast retrieval times
Composed of metallic rather than plastic disks Platters – rigid metallic, stacked one on top of another A cylinder (Key Term) runs through each track of a stack of platters Fast information storage and retrieval Read-write head is .000001 inch above surface
Head crashes occur when the read-write head contacts with the disk surface or with particles on the disk's surface Head crashes are now rare A smoke particle, human hair, or fingerprint could cause a head crash
Located inside the system unit Used for storing the operating system, other programs, and large data files You should perform routine maintenance and periodically backup all important files
Capacity limited only by number of removable devices you want to add to your system; used to complement internal hard disk. Includes USB, FireWire, eSATA external disk enclosures PC Card hard disk (Key Term) available for notebooks with a capacity of up to 5 GB
Disk caching Uses hardware and software to anticipate data needs; performs function similar to RAM caching; improves processing by acting as a temporary high-speed holding area between a secondary storage device (Key Term) and the CPU Frequently used data is stored in memory; when needed, the access time is much faster Redundant arrays of inexpensive disks (RAID) Groups of low cost hard-disk drives grouped together using networks and special software Performs as a single large-capacity disk; but faster than a single disk of comparable size Often used by Internet servers and large organizations File compression and decompression Increase storage capacity Reduce space required for storage; reduce up to ¼ of original size WinZip and UltimateZip are well-known programs, and you can also use utility programs in Windows XP
Use laser technology. CD (Key Term) and DVD (Key Term) are optical disk formats. Compact, high capacity form of permanent storage (up to 50 gigabytes of data) Optical discs are read by an optical disc drive Laser beam writes by creating a pattern of pits (holes) and lands (flat areas) to encode data bits Laser beams reflect off the pits and lands to read the data Rotational speed determines how fast data can be transferred from the CD Optical disks come in many different sizes Most common is 4 ¾ inches Stored in a protective case called jewel boxes
CD stands for compact disc Standard on most computers; can store from 650 MB up to 1 GB Speed determines how fast data can be transferred Read only: CD-ROM Commercial music CD Read only means it cannot be written on or erased Used to distribute large databases and references Write once: CD-R (CD-recordable) Used to archive data or to record music downloaded from the Internet Rewriteable: CD-RW Known as erasable optical disks (Key Term) Can be changed Used to create and edit multimedia presentations Ideal for use as permanent data archives for essential company information
Blu-ray, also known as BDs Have a capacity of 25 to 100 gigabytes Blu-ray has seemingly won the battle as the standard high definition video disc
Solid state drives are faster and more durable (no moving parts) than hard drives Require less power Contain solid state memory instead of magnetic disk to store data Flash memory cards are one type of solid state device.
Mass storage devices that support enterprise storage systems are File servers (Key Term) – dedicated computer with very large storage capacities that provide user access to fast storage and retrieval of data RAID systems (Key Term) – larger versions of the specialized devices discussed earlier in this chapter that enhance organizational security by constantly making backup copies of files moving across the organization’s networks Tape library (Key Term) – device that provides automatic access to data archived on a large collection or library of tapes DVD-ROM and CD-ROM jukeboxes (Key Term) – provide automatic access to a large collection or library of optical disks Organizational Internet Storage (Key Term) – high-speed Internet connection to a dedicated remote organizational Internet drive site
Are there downsides? Could your personal video log be used to incriminate you in a court of law? Could someone else’s video log be an invasion of your right to privacy?
Have students turn to the end of Chapter 8 in their textbooks to view the same “Open-Ended” questions/statements
Have students turn to the end of Chapter 8 in their textbooks to view the same “Open-Ended” questions/statements