Storage Hardware Chapter 4 Preserving Data and Information © The McGraw-Hill Companies, Inc., 2000

Ch 4© The McGraw-Hill Companies, Inc., CCI Overview Storage fundamentals Tape storage Diskette storage Hard disk storage Optical storage Backup

Ch 4© The McGraw-Hill Companies, Inc., CCI Storage Fundamentals What is the difference between primary and secondary storage? What are the basic types of files?

Ch 4© The McGraw-Hill Companies, Inc., CCI Save Your Files Save your files to secondary storage One can think of file storage as a file cabinet –drawers –folders Calling up a file actually calls up a copy of a file, until it is modified or saved

Ch 4© The McGraw-Hill Companies, Inc., CCI Save Your Files Helpful hints –you are in charge of file organization –electronic file organization is easier that physical file organization use names to keep track of versions organize in folders the way you reference and use files backup, backup, backup

Ch 4© The McGraw-Hill Companies, Inc., CCI Common Elements of Storage Technology Amount of data in a file is usually expressed in kilobytes or megabytes Total amount of data in a storage area that includes multimedia/video maybe measured in gigabytes

Ch 4© The McGraw-Hill Companies, Inc., CCI Storage Technology Retrieving files into RAM is called reading –loading an application –opening a file

Ch 4© The McGraw-Hill Companies, Inc., CCI Storage Technology (continued) writingCopying data from RAM onto a secondary storage device called writing Sequential storage –magnetic tape –random accessing sequential data is time consuming

Ch 4© The McGraw-Hill Companies, Inc., CCI Storage Technology (continued) Direct access storage –faster than sequential access Indexed-sequential –stores data sequentially –are indexed –a combination of sequential and direct access storage methods

Ch 4© The McGraw-Hill Companies, Inc., CCI File Types Program files –source files –executable files Data files –also called document files –contain only data

Ch 4© The McGraw-Hill Companies, Inc., CCI File Types (continued) ASCII files –text-only –ASCII code is one of the most common codes Image files –digitized graphics in such formats as GIF, JPEG

Ch 4© The McGraw-Hill Companies, Inc., CCI File Types (continued) Audio and video files –digitized sound and video –WAV, MP3, MPEG, AVI

Ch 4© The McGraw-Hill Companies, Inc., CCI File Descriptors Files have unique names Windows-based systems have a three- character extension Macintosh, UNIX, and Linux-based systems do not use extensions

Ch 4© The McGraw-Hill Companies, Inc., CCI File Descriptors: Identification

Ch 4© The McGraw-Hill Companies, Inc., CCI Tracking files File tables –File Allocation Tables (FAT) keep track of where data is stored each type must be coordinated with hard disk size –FAT or FAT-16, Windows 95 –FAT-32, Windows 95 OSR/2, Windows 98 and later –NTFS, Windows NT –HPFS, IBM OS/2

Ch 4© The McGraw-Hill Companies, Inc., CCI File Management Copying Renaming Deleting –some corporations do not allow deletion of files by individuals Printing Import/Export

Ch 4© The McGraw-Hill Companies, Inc., CCI Tape Storage Reels for mainframes Cartridge tape units or tape streamers –QIC quarter-inch tapes up to 20 GB

Ch 4© The McGraw-Hill Companies, Inc., CCI Tape Storage Options DAT –Digital audio tape up to 24 GB DLT –Digital linear tape up to 70 GB

Ch 4© The McGraw-Hill Companies, Inc., CCI Diskette Storage Diskette or floppy disk –3 ½” = 1.44 MG are inexpensive –called HD high-density

Ch 4© The McGraw-Hill Companies, Inc., CCI Large Capacity Diskettes Zip (100 MB and 250 MB) Imation SuperDisks or LS-120 (120 MB) and Sony HiFD (200 MB) –drives can accept 1.44 MB

Ch 4© The McGraw-Hill Companies, Inc., CCI Diskette functionality Tracks and sectors Unformatted Formatted –or initialized (Macintosh) –formatting will erase all previous data on disk Write-protected –two open holes

Ch 4© The McGraw-Hill Companies, Inc., CCI Care and Feeding of Diskettes Don’t touch diskette surfaces Be careful with the protective plate –best to carry within a plate diskette holder Handle gently Avoid sun and heat Don’t leave a diskette in the drive

Ch 4© The McGraw-Hill Companies, Inc., CCI Hard Disks What are the characteristics of hard disks, and what types of hard disks are available?

Ch 4© The McGraw-Hill Companies, Inc., CCI Hard Drive Characteristics Common 10 to 20 GB size 10 GB hard drive stores approximately 3 million pages of information Multimedia and graphics-oriented requirements will quickly fill up any hard drive Tightly sealed disks covered with magnetic material

Ch 4© The McGraw-Hill Companies, Inc., CCI Internal Hard Drives Internal to system –connected via IDE, SCSI, or controller (host adapter) interface to motherboard –some computers can support two internal hard drives

Ch 4© The McGraw-Hill Companies, Inc., CCI EIDE EIDE or Enhanced Integrated Drive Electronics –each port can support a CD-ROM or optical disk drive –native EIDE 16.6 MG transfer rate –Ultra DMA (direct memory access) if drive and motherboard built for these newer standards uses same EIDE port 33 MG per second 66 MG per second, using newer cable type

Ch 4© The McGraw-Hill Companies, Inc., CCI SCSI SCSI (pronounced “scuzzy”) –small computer system interface –used first on Macs –used on PCs with SCSI adapter card or built-in SCSI –maximum SCSI transfer rates vary from 20 to 160 MB depending on standard

Ch 4© The McGraw-Hill Companies, Inc., CCI EIDE or SCSI? With Ultra DMA 66 for EIDE ports, there is no longer a simple answer to which type is faster - EIDE or SCSI Depends on the standard being used, type of data being recorded, and traffic along the SCSI chain

Ch 4© The McGraw-Hill Companies, Inc., CCI Hard Disk Variations External hard drives –via parallel port, SCSI interface, or USB interface Removable disks –also called removable hard disks –SyQuest SyJet –Iomega’s Zip and Jaz

Ch 4© The McGraw-Hill Companies, Inc., CCI Using Hard Disk Technology Virtual memory –Hard disk space is used to extend main memory (RAM) Removable packs –up to 20 hard drive platters for large system use

Ch 4© The McGraw-Hill Companies, Inc., CCI More HD technology Fixed disk storage –up to 100 disks in one cabinet RAID –redundant array of inexpensive disks –storage system with fail-safe system technology

Ch 4© The McGraw-Hill Companies, Inc., CCI Hard Disk Future MR Head –separates read and write functions into two physically separate heads –will improve performance in the foreseeable future

Ch 4© The McGraw-Hill Companies, Inc., CCI Optical Disks What are optical disks, and how are they used? Uses laser technology, rather than magnetic oxide to store data

Ch 4© The McGraw-Hill Companies, Inc., CCI Types CD-ROM –compact-disk-only memory CD-R –compact disk-recordable –write once only CD-RW –compact disk-rewritable

Ch 4© The McGraw-Hill Companies, Inc., CCI CD Advantages CD-R and CD-RW drives can read CD- ROMs Better quality audio than traditional tape CD-R and CD-RW can be used for system and file backup

Ch 4© The McGraw-Hill Companies, Inc., CCI More Types DVD/DVD-ROM –Digital video disk –Digital versatile disk –Stores up to 17 GB –rewritable DVD types are being developed –all should be able to play any CD

Ch 4© The McGraw-Hill Companies, Inc., CCI DVD Advantages More storage capacity Better audio Better video Future recordable and rewriting capabilities

Ch 4© The McGraw-Hill Companies, Inc., CCI Backup Why backup? All disks/systems crash –it is just a matter of time for hard disks, floppies, and systems –large systems survive because they are sustainable since all disks crash, automatic full-backups and incremental backups insure minimum interruption of business operations

Ch 4© The McGraw-Hill Companies, Inc., CCI Why do they crash? Systems –complexity is inherent in systems Hard drives, floppies, and storage media –these are physical items that wear out –with average use tape lasts 5 to 15 years Zip disks 10 years floppies 5 to 10 years

Ch 4© The McGraw-Hill Companies, Inc., CCI Other Forms of Secondary Storage Flash memory flash RAM no moving parts up to 100 MB Advanced storage technology manufacturers pushing physical limits IBM developing optical system that can store 350 million bits a square inch NEC physicists developing storage media that may be atoms thick