Chapter 8 Secondary Storage

Competencies (Page 1 of 2) Distinguish between primary and secondary storage Compare internal and external hard disks Describe ways to improve hard-disk operations, including disk caching, redundant arrays of inexpensive disks, and data compression and decompression Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Competencies (Page 2 of 2) 8-3 Competencies (Page 2 of 2) Discuss solid-state storage devices including flash memory and USB drives Discuss the different types of optical disks Describe Internet drives, floppy disks, and magnetic tape Discuss mass storage, floppy disks, and mass storage devices Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Introduction Data storage has expanded from text and numeric files to include digital music files, photographic files, video files, and much more. These new types of files require secondary storage devices with much greater capacity than floppy disks. In this chapter, you will learn about the many types of secondary storage devices including their capabilities and limitations. Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Storage RAM Primary storage Secondary storage 8-5 Storage Primary storage Volatile storage Temporary storage Secondary storage Nonvolatile storage Permanent storage Secondary storage characteristics Media Capacity Storage devices Access speed 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 RAM Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Secondary Storage Devices 8-6 Secondary Storage Devices Most desktop microcomputer systems have hard disks and optical disk drives Are used to save, back up, and transport data files and programs Optical disks – large storage capacity (Key Term) Hard disk – large storage capacity and fast retrieval times

Hard Disks Use thicker, metallic platters for storage Faster than a floppy diskette Large capacity Sensitive instruments There are three types of hard disks: Internal Hard Disk External Hard Disks Digital Versatile Discs Performance Enhancements 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Materials that Cause a Head Crash 8-8 Materials that Cause a Head Crash Head crash is a disaster for a hard disk 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 Return

Internal Hard Disk Located inside system unit Designated as the C drive Advantages over other removable media Capacity Access speed 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 Return Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

External Hard Disks Removable hard disks Used to complement internal hard disk Capacities of 20 to 500 GB Hard-disk cartridge Capacity limited only by number of cartridges; used to complement internal hard disk. PC Card hard disk (Key Term) available for notebooks with a capacity of up to 5 GB PC Card Hard Disks Return Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Digital Versatile Disks DVD stands for digital versatile disk or digital video disk DVD-ROM DVD+R and DVD-R DVD+RW, DVD-RW, and DVD-RAM Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Performance Enhancements Disk caching Redundant arrays of inexpensive disks (RAID) File compression and decompression 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Optical Disks Hold over 50 gigabytes of data Attributes Three types Lands Pits Three types Compact Disc (CD) Digital Versatile Disc (DVD) Hi-Def Disc 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Compact Disc Optical format From 650 MB to 1 GB capacity Rotation speeds vary Three basic types Read only: CD-ROM Write once: CD-R Rewriteable: CD-RW 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 Return Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Digital Versatile Disc Digital Versatile Disc or Digital Video Disc (DVD) Similar to CDs, but can store more data Three basic types Read only: DVD-ROM Write once: DVD+R; DVD-R Rewritable: DVD+RW; DVD-RW; DVD-RAM DVD-ROM Known as DVD players (Key Term) Used for videos DVD-R and DVD+R Two competing write once formats Write once format Used to create permanent archives for large amounts of data and to record videos DVD-RAM or DVD-RW – rewritable version DVD-RW DVD+RW DVD-RAM Each format has a unique way of storing data; older DVD players can’t read all formats but the new DVD players can Rapidly replacing the CD rewritable drives Use to store video from camcorders and developing large multimedia presentations that include extensive graphics and video Return Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

High-Definition Disc Next generation of optical disc Far greater capacity than DVDs Three basic types Read only Write once Rewriteable Two competing hi def formats HD DVD Blu-Ray HD DVD stands for high definition DVD Capacity of 15 to 45 gigabytes Advantage is that current manufacturing plants producing standard DVD discs can be easily converted to mass produce HD DVD discs Blu-Ray, also known as BDs Have a capacity of 25 to 50 gigabytes Cannot be easily manufactured in existing DVD disc manufacturing plants The two formats appear that they will not be compatible with each other Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Other Types of Secondary Storage Solid-state storage Internet hard drives Magnetic tape Solid-state storage No moving parts Reliable, but expensive Requires less power Internet hard drives (Key Term) Low cost Flexibility to access information from any location using the Internet Slower access speed Magnetic tape Slower sequential access (Key Term) Stores data and programs Used for making backups of data Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Ipods and Videos From The Internet The Internet can be used as a medium to locate and play music and videos A user can create compact discs, or transfer music to a portable player Requirements Software Hardware Internet Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Solid-State Storage Flash memory cards Widely used in notebook computers Used to record MP3 music files Flash memory card Flash memory cards are one type of solid state device. Return Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Internet Hard Drives Known as i-drive or online storage 8-20 Internet Hard Drives Known as i-drive or online storage Low cost and can access information from any location using the Internet Oriented to either businesses or individuals These are Web sites that provide storage space Not used for storing highly personalized or sensitive information Return

Magnetic Tape External storage Provides sequential access Information stored in sequence Slower than disks which provide direct access Magnetic tape streamers or tape cartridges used by both mainframes and microcomputers Sequential access because they have to be fast forwarded or rewound before a specific location can be reached A common sequential access method of permanent storage method Common form of data backup in companies with larger computer systems; magnetic disk offer fast, direct access to data programs Two forms of tape storage Magnetic tape streamers Backup tape cartridge units used with microcomputer systems Capacities range from 120 MB to 5 GB At one time, mainframe computers used magnetic tape reels (Key Term) exclusively Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Mass Storage Devices Mass storage refers to the tremendous amount of secondary storage required by large organizations Mass storage devices are specialized high-capacity secondary storage devices Enterprise storage system promotes efficient and safe use of data across networks within organizations 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 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Careers In IT Software engineers analyze users’ needs and create application software General employer requirements Bachelors degree in computer science Extensive knowledge of computers and technology Good communication and analytical skills Software engineers can expect to earn an annual salary of $63,000 to $98,500 Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

A Look to the Future Your Entire Life Recorded on a Single Disk Future secondary storage disks could eventually store one terabyte Experiments with three dimensional storing Video of an entire life Technology is being used to rapidly scan photos and videos 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? Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Discussion Questions (Page 1 of 2) Compare solid-state storage and hard disks. What are the three types of hard disks? Describe three ways to improve hard disk performance. What are the two most common optical disk formats? What is Blu-Ray? Describe the basic types for each format. Have students turn to the end of Chapter 8 in their textbooks to view the same “Open-Ended” questions/statements Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.

Discussion Questions (Page 2 of 2) Discuss Internet hard drives and magnetic tape. What are the advantages and disadvantages of each? Discuss mass storage, enterprise storage systems, and mass storage devices. Have students turn to the end of Chapter 8 in their textbooks to view the same “Open-Ended” questions/statements Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.