Chapter 8 Secondary Storage

Competencies (Page 1 of 2) Distinguish between primary and secondary storage Describe the traditional floppy disk and compare it to high capacity floppy disks Compare internal hard disks, hard-disk cartridges, and hard-disk packs Page 230

Competencies (Page 2 of 2) Describe ways to improve hard-disk operations, including disk caching, redundant arrays of inexpensive disks, and data compression and decompression Discuss the different types of optical disks; mass storage Describe solid-state storage, Internet drives, and magnetic tape Discuss mass storage and mass storage devices Page 230

Secondary Storage Devices Most desktop microcomputer systems have floppy disks, hard disks, and optical disk drives Are used to save, back up, and transport data files and programs Floppy disk – inexpensive and removable Optical disks – large storage capacity (Key Term) Hard disk – large storage capacity and fast retrieval times Page 231

Storage RAM Primary storage Secondary 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 (Key Term) – 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 (Key Term) – measures the amount of time required by the storage device to retrieve data and programs Writing (Key Term) – process of saving information to the secondary storage device RAM Page 232

Floppy Disks Portable or removable storage media Typically used to store and transfer small word processing, spreadsheet, and other types of files Floppy disk drives (FDD) Store data and programs Retrieves data by reading electromagnetic charges Also called flexible disks and floppies Page 232

Traditional Floppy Disk Most common type is 2HD “two-sided, high-density” Attributes Shutter Labels Write-protection notch Tracks Sectors Floppy disks are removable storage media. Today’s standard is 1.44 MB 3½-inch disk (Key Term). Data recorded in rings called called tracks; tracks divided into wedge-shaped sections called sectors Most disks (Key Term) manufactured currently preformatted w/tracks and sectors While called floppy, actually pieces of flat Mylar rotating within a hard plastic jacket The bits of data are represented by the presence or absence of magnetic charges Storage capacities range from 360 KB to 1.44 MB Write-protect notch or window to prevent inadvertent erasure or write-over Density (Key Term) refers to how tightly the bits can be packed next to one another; common density is 2HD A shutter on the disk slides to the side to expose the recording surface Labels provide an area to write or document the contents of the disk Page 233

High Capacity Floppy Disks Known as a floppy-disk cartridge Require special disk drives Most widely used is the Zip disk 100 MB, 250 MB or 750 MB capacity Used to store multimedia, database, large text, and spreadsheet files Floppy-disk cartridge can also be referred to as a high-capacity disk (Key Term) Zip disks – usually manufactured by Iomega; 100 MB, 250 MB, or 750 MB worth of storage; requires own drive HiDF disks – usually manufactured by Sony Corp; 200 MB or 750 MB capacity Biggest advantages: can use HiDF disk in floppy drive; popular with notebooks Super disks – usually manufactured by Imation; 120 MB or 240 MB capacity; SuperDisk disk drives can use standard floppy disks Zip disks – 100 MB, 250 MB or 750 MB HiFD disks - 200MB or 720MB SuperDisks – 120 MB or 240 MB Page 234

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 Hard-disk cartridge Hard-disk pack 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 An internal hard disk is also known as a fixed disk (Key Term) Page 234

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 Page 235

Internal Hard Disk Located inside system unit Known as a fixed disk Designated as the C drive Advantages over floppies Capacity Access speed Located inside the system unit; also known as fixed disk Used for storing the operating system, other programs, and large data files You should perform routine maintenance and periodically backup all important files Return Page 235

Hard-Disk Cartridges Removable hard disks Used to complement internal hard disk Capacities of 20 to 100 GB Iomega is one of the most widely used Hard-disk cartridge PC Card Hard Disks Capacity limited only by number of cartridges; used to complement internal hard disk. Popular Vendor: Peerless disks from Iomega PC Card hard disk (Key Term) available for notebooks with a capacity of up to 5 GB Return Page 235

Hard-Disk Packs Removable hard disk Massive storage capacity Common in mainframes Are utilized by banks and credit card companies Massive storage capacity Common in mainframe systems Composed of a larger number of platters, resembling a stack of record albums Most platters offer read-write surfaces on top and bottom Access time – time between the computer’s request for data from secondary storage and the completion of the data transfer; usually access time is faster with this type of secondary storage Return Page 236

Performance Enhancements Disk caching Redundant arrays of inexpensive disks (RAID) File compression and decompression RAID storage device 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 PKZip are well-known programs, and you can also use utility programs in Windows XP Page 237

Optical Disks Hold over 17 gigabytes of data Attributes Three types Lands Pits Rotational speed 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 17 gigabytes of data) Optical discs are read by an optical disc drive (Key Term) 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 Page 238

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) Known as CD burners (Key Term) 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 Most newer CD-ROMS are multiread, (Key Term) or able to read both CD-R and CD-RW discs Return Page 239

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 Page 239

Hi-Def 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 30 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 Page 240

Other Types of Secondary Storage Solid-state storage Internet hard drives Magnetic tape Solid-state storage No moving parts Reliable, but expensive 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 Page 241

Solid-State Storage Flash memory cards Key chain hard drives Widely used in notebook computers Used to record MP3 music files Key chain hard drives Key chain flash memory devices or flash drives Connects to a USB port Flash memory cards Key chain hard drives have recently been introduced Very compact Worn as a necklace or on a key ring Connect to a USB port Predicted that they will replace the floppy disk for transporting data Capacities up to 1 GB Key chain flash memory Return Page 241

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 Page 244

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 Page 244

Music From The Internet The Internet can be used as a medium to locate and play music A user can create compact discs, or transfer music to a portable player Requirements Software Hardware Internet Page 242

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 Page 245

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 $50K to $85K Page 246

A Look to the Future Your Entire Life Recorded on 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? Page 247

Discussion Questions (Page 1 of 2) Discuss the traditional and high-capacity floppy 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 hi def? 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 Page 254

Discussion Questions (Page 2 of 2) Discuss solid-state storage, 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 Page 254