6 Secondary Storage computing ESSENTIALS     Copyright 2003 The McGraw-Hill Companies, Inc.Copyright 2003 The McGraw-Hill Companies, Inc.

Competencies computing ESSENTIALS     Different types of media Floppy disks Hard disks Performance enhancements Optical disks Specialized media Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Secondary Storage Stores information Non-volatile, permanent storage Characteristics Media Capacity Access time Secondary storage is – stores programs and data nonvolatile as opposed to volatile (temporary) storage (RAM) which is lost when power shut off to computer. Media – actual physical material that hold data Capacity – amount of data the storage medium can hold Access time – amount of time to retrieve and write data Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Types of Storage Media Types widely used today Floppy disks Hard disks Optical disks Magnetic tape Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Floppy Disks Portable and removable Flat circular Mylar media Magnetic charge on metal oxide film coating Standard 2HD 1.44 MB Parts Tracks Sectors Floppy disks are removable storage media. Today’s standard is 2HD (Double sided, double density) 1.44 MB. Data recorded in rings called called tracks; tracks divided into wedge-shaped sections called sectors Pieces of floppy flat Mylar rotating within a hard plastic jacket The bits of data are represented by the presence or absence of magnetic charges Write-protect notch or window to prevent inadvertent erasure or write-over Limited capacity today. Many media files far exceed the capacity of standard floppy disks Copyright 2003 The McGraw-Hill Companies, Inc.

High Capacity Floppy Disks computing ESSENTIALS     High Capacity Floppy Disks Floppy disk cartridges Zip Disks 250 MB SuperDisks 120 MB HiFD disks 200 MB Zip disks – usually manufactured by Iomega 100 to 250 MB worth of storage Requires own drive Drive can only read/write to Zip disks Super disks – usually manufactured by Imation 120 MB capacity; popular with notebooks Drives can also read/write standard 2HD disks HiDF disks – usually manufactured by Sony Corp 200 MB capacity Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Hard Disks Metallic disks Fast retrieval, greater capacity Read/write heads ride cushion of air .000001” thick Three types Internal hard disk Hard-disk cartridge Hard-disk pack Composed of metallic rather than plastic disks Fast information storage and retrieval Read-write head is .000001 inch above surface! Any particle of dirt can cause a head crash – scratch across disk See next slide for good graphic of “space” Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Head crashes occur when the read-write head contacts the disk surface or particle of dirt on the disk surface The disk and the disk head will likely be damaged causing data to be lost A smoke particle, human hair or fingerprint could cause a head crash Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Internal Hard Disk Inside system unit Non-removable or portable Great capacity Over 100 Gigabytes Fast access speed Located inside the system unit; also known as fixed disk Used for storing the operating system, other programs and large data files One or more metallic platters sealed inside a container Container holds Motor for rotating the disks Access arm and read-write heads Advantages over floppy disks 56,000 floppies worth of information Speed (twenty times the speed) Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Hard-disk Cartridges Portable, removable Complement internal hard drive JAZ from Iomega SPARQ from SyQuest PC Card Hard Disks Laptop computers Capacity limited only by number of cartridges Used to complement internal hard disk. Particularly useful for securing data on the drive – can be removed and locked up. Typical capacity = 2 to 20 GB Popular vendors: Iomega and SyQuest PC Card hard disks – hard disk cartridges for notebook and laptop computers. Typical capacity up to 10 GB IBM’s Microdrive Hitachi’s PC Card hard drive Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Hard-disk Packs Used in mainframes Removable Resemble stack of vinyl records Multiple read/write heads Massive storage capacity Fast access time 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 Multiple heads move together, but only one head is active at a time. Top and bottom outside surfaces of the pack are not used, so a pack of 11 disks gives 20 recording surfaces. Massive storage capacity 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 Copyright 2003 The McGraw-Hill Companies, Inc.

Performance Enhancements computing ESSENTIALS     Performance Enhancements Improving performance of hard disks Disk caching Redundant Arrays of Inexpensive Disks (RAID) File compression and decompression Disk caching Uses hardware and software to anticipate data needs 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 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 Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Optical Disks Very large capacity Up to 17 gigabytes Use reflected light projected by a laser Lands and Pits represent 1’s and 0’s Formats Compact Disk (CD) Digital Versatile Disk (DVD) DataPlay uses laser technology. Compact, high capacity form of permanent storage 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 CD, DVD, and DataPlay are optical disk formats. Three basic types of optical discs CD-ROM, CD-R and erasable optical discs, or CD-RW Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Compact Disks Widely used format today Can store from 650 MB to 1 GB Rotational speed = data transfer time Types of CDs CD-ROM CD-R CD-RW CD drives come standard on computer systems today. High capacity of data is stored on them. Typically they are between 650 MB to 1 Gigabyte. A CD drives rotational speed is important because that determines how fast data can be transferred from the disk. For example: A 24X CD drive can transfer 3.6 MB per second A 32X CD drive can transfer 4.8 MB per second Data on a CD is written in one continuous stream, similar to a phonograph record groove. However, the data stream begins in the center of the disk and proceeds outwards. Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     CD-ROM Compact Disc-Read Only Memory Cannot be written to or erased Similar to commercial music CDs Used often to distribute large databases or references Compact disc-read-only memory Used for distribution of large data such as Grolier Electronic Encyclopedia - nine million words and 1900 pictures Large software packages like MS Office Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     CD-R & CD-RW CD-Recordable Written to once Custom made music CDs CD-ReWritable Erasable CD Ideal for multimedia presentations Stands for CD-Recordable Also known as WORM, or write once, read many Ideal for use as permanent data archives for essential company information CD changers or CD jukeboxes can facilitate rapid access to large amounts of information Also known as rewritable optical discs Unlike CD-R, these discs can be written on numerous times Most common technology is magneto-optical (MO) disc drive, combining magnetic and optical technologies Capacities up to 1,000 megabytes (a gigabyte) Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     DVD Digital Versatile Disk Rapidly replacing CDs Higher capacity 17 times the capacity of a CD 4.7 gigabytes to 17 GB per disk Predicted to replace CD; not quite there – but in great demand and highly used – especially for movies and games Most computers are beginning to come with DVD drives standard Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     DVD Types DVD types DVD-ROM Read only memory DVD-R Recordable DVD-RAM or DVD-RW Competing rewritable formats DVD-ROM - provide high quality, movie length videos 4.7 GB storage; seven times a regular CD DVD-R - consumer recordable version just getting started 4.7 GB storage DVD-RAM or DVD-RW - rewritable version 2.6 to 5.2 GB storage Up to 17 gigabytes of capacity, fourteen times CD Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     DataPlay Optical write-once format Similar to CD-R Size of a quarter Used for special applications Storing digital photographs Storing music for portable players Small optical disks with a capacity of about 500 MB. About the size of a quarter. Used for small devices such as digital cameras or portable music players. Copyright 2003 The McGraw-Hill Companies, Inc.

Other Secondary Storage Types computing ESSENTIALS     Other Secondary Storage Types Complement other secondary storage devices Specialized device types Magnetic tape Internet hard drives Solid state storage The basic secondary storage options don’t compete so much as complement each other. Each is suited to their particular tasks. Magnetic tape, Internet hard drive, and solid state storage further complement the basic types. Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Magnetic Tape Sequential access Commonly used for backing-up data Very large capacity Types of magnetic tape Tape cartridges Magnetic tape reels Sequential access because they have to be fast forwarded or rewound before a specific location can be reached. A common sequential access method of Two forms of tape storage Magnetic tape cartridges, also called magnetic tape streamers Magnetic tape reels Tapes are run on magnetic tape drives or magnetic tape units Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Magnetic Tape Types Tape cartridges Backup tape for microcomputer Capacities range from 120 MB to 5 GB Digital audio tape (DAT) Tape reels Minicomputer and mainframe 1/2 inch wide and 1/2 mile long Stores 1600 to 6400 cpi Backup tape cartridge units used with microcomputer systems Typical capacities range from 120 MB to 5 GB Advanced forms use digital audio tape (DAT) Copyright 2003 The McGraw-Hill Companies, Inc.

Internet Hard Drive and Solid State computing ESSENTIALS     Internet Hard Drive and Solid State Internet hard drive Free or low-cost storage on the Web Access information from any location Access time is greater Solid-state storage No moving parts Flash memory cards Internet hard drive are located on special secure websites that offer low-cost alternative to local storage. Advantages: The data can be accessed from anywhere on the Web. Low cost compared to buying a high capacity device. Disadvantages: Because it must travel through the Web, access time can be slow. User is dependent on accessibility to the website. Dependent on the service provider for security. Solid State Storage Similar to computer RAM. No moving parts of the media. Reliable, requires less power Expensive Flash memory cards Used in digital cameras to store images, or in MP3 devices to record music and transfer them to other computer media. Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     A Look to the Future Blue laser light optical devices Aimed more accurately Can increase storage capacity to 27 GB per standard optical disk New players will likely play both Current DVD and CD players and recorders use red light lasers. Blue light lasers can be aimed more accurately and compactly. More compact means more data storage in same amount of space. Since current players would not be able to read new disk format, new players may incorporate both red and blue lasers. Copyright 2003 The McGraw-Hill Companies, Inc.

Copyright 2003 The McGraw-Hill Companies, Inc. computing ESSENTIALS     Copyright 2003 The McGraw-Hill Companies, Inc.