Intro to Info Tech Storage Devices This presentation

Intro to Info Tech Storage Devices This presentation can be viewed on line at: Copyright 2003 http: //web. fscj. edu/Janson/cgs 1060/wk 08. Storage. ppt by Janson Industries 1

Objectives n n Explain the various devices Explain and compare the relative advantages and disadvantages 2 Copyright 2012 by Janson Industries

Storage Devices n n Hold data and instructions, can also hold output Comprised of a device and media u n n Device writes to and reads from a particular medium Been around since beginning of computers Early medium – punch cards 3 Copyright 2012 by Janson Industries

Storage Devices n n Measured two ways u Speed (access/write/rewrite) u Capacity Also, compared according to u Portability – can medium be moved to another device u "Rewritability" – once written to can medium be it be changed 4 Copyright 2012 by Janson Industries

Storage Devices n Secondary storage vs. Internal storage (Main Memory/MM) u Slower access F u SS measured in microseconds, PC MM nanoseconds Holds much more F PC MM measured in GB, SS TB 5 Copyright 2012 by Janson Industries

Storage Device Types n Magnetic Disks n Optical Disks n Other 6 Copyright 2012 by Janson Industries

Magnetic Disks n Surface can be magnetized and demagnetized u n Magnetic state represents a 0 or 1 Surface broken up into u Tracks u Pie shaped sections u Sectors F F Copyright 2012 by Janson Industries Tracks and sections numbered This provides identifier for sectors 7

Magnetic Disks n 2 types u Floppy disk/floppy drive F u Portable media Hard disk/hard drive F F Some are/some are not portable Most desktop PCs have a single unit where medium can't be separated and moved to another device 8 Copyright 2012 by Janson Industries

Floppy Disks n Historically, different sizes u 3. 5, 5. 25, 8 u 3. 5 holds about 1. 44 megs n Single vs. double sided n Zip disks hold a lot more 9 Copyright 2012 by Janson Industries

Hard Disk n n Made up of multiple inflexible platters Read/write heads u n One for each platter surface How heads and platter work: u u u Heads 2 millionths of an inch over surface Sense the magnetic state of platter surface Head crash – Bad! 10 Copyright 2012 by Janson Industries

Hard Disk n n How the whole thing works u Arm extended to correct track u Platter spun so correct sector is under read/write head u Surface read and value sent via circuitry through the arm http: //www. youtube. com/watch? v=9 e. MWG 3 fwi. EU 11 Copyright 2012 by Janson Industries

Hard Disk n With hard disks, different units of storage u u n To make access faster try to store info u u u Copyright 2012 by Janson Industries Cluster: group of adjacent sectors, smallest unit of allocatable storage Cylinder: all same tracks on different platter surfaces In one track If data larger than a track, store in same cylinder Why? 12

Other Hard Disks n External hard disks u u n One unit separate from system unit Plugs into USB port Capacity in TBs Some more portable than others Removable HD u u Very portable Machines must have a removable HD bay 13 Copyright 2012 by Janson Industries

Other Hard Disks n Miniature HDs u u n Often built into a mobile device like camera, headphones Pocket HD has more capacity than a thumb Large systems have many hard drives u Will have disk controller(s) F F Specialized chip that manages communication with disk drives Decreases work for the CPU 14 Copyright 2012 by Janson Industries

Optical Disks n n n Surface of the disk is altered to affect it's reflectivity To read, a beam of light is shot onto the surface The amount of light reflected will represent a 0 or 1 15 Copyright 2012 by Janson Industries

Optical Disks n Compared by their u u Sidedness Capacity Speed Read/Write capability F F n Reading is called ripping Writing is called burning 2 major types u u CDs DVDs 16 Copyright 2012 by Janson Industries

Compact Discs n n Usually u One sided u Capacity 650 MB – 1 GB Different types determined by the read/write capability u CD-ROM u CD-RW 17 Copyright 2012 by Janson Industries

Compact Discs n n CD-ROM (Read Only Memory) u Single session – can write to disc once u Can read many times u Used to be called a WORM disc What good is this type of CD? u S/W mfgs write to these type of disks and then distribute u Users can't inadvertently erase the application 18 Copyright 2012 by Janson Industries

Compact Discs n n CD-R (Read) u Multi-session – can write to one portion of disk and then later to another u Can read many times u Can't erase what is written CD-RW (Rewritable) u Can write, read, erase, and rewrite to disc 19 Copyright 2012 by Janson Industries

CD Drives n Compared by u The type of discs they support F Can they read and/or write u Read, write, rewrite speed u Measured like this: F F F Read 128 X Write 64 X Rewrite 24 X 20 Copyright 2012 by Janson Industries

DVDs n Digital Versatile Disc u Holds more than CDs F u Capacity depends on whether F F F u 4. 7 GB to 100 GB Single or double sided Regular or high capacity DVD Single or multiple layers Battle for high capacity DVD format between Blu-ray and HD F Blu-ray won! (BD) 21 Copyright 2012 by Janson Industries

Reading and Writing to DVDs n For Blu-ray, two types of discs u u n Regular discs are more complicated u u n BD-R is read only BD-RE can read and write DVD+R and DVD-R are read only DVD+RW, DVD-RW, and DVD+RAM can read and write The DVD drive must support the particular DVD format u Most DVD drives support CDs 22 Copyright 2012 by Janson Industries

Reading and Writing to DVDs n DVD-R approved by DVD Forum u n DVD+R supported by the DVD+RW Alliance. u n Includes: Mitsubishi, Sony, Philips, Hitachi, Time Warner and others Includes: Sony, Yamaha, Philips, Dell, HP and others Differences Defects management u How DVDs are formatted and rewritten u What TV DVD players will play them u For computer backups, either one will do Copyright 2012 by Janson Industries u 23

Other Storage n Tape u A magnetic ribbon u Two formats: F F u Only provides sequential access F u Cartridge Reel to reel Discs provide direct access Tapes often used for back up 24 Copyright 2012 by Janson Industries

Other Storage n n Flash memory cards u Flash memory (i. e. chip based) u Used in notebooks, cameras, PDAs u Need a special drive/slot in device USB Flash drives (aka Thumb drives) u Comprised of both media and device u Don't need special drive/slot, just need a USB port 25 Copyright 2012 by Janson Industries

Other Storage n Smart cards u Chip based memory u Can also process information F F n Copyright 2012 by Janson Industries Holds a defined amount of money You buy something, that amount is decreased Online u Can access files from anywhere u Give others access u Many are free 26

Online Storage n Three big players (8/2015) u Google Drive F u One. Drive -formerly Skydrive (MS) F u 2 GB free, 1 TB $7. 99/month All offer other ways to get more u Copyright 2012 by Janson Industries 15 GB free Dropbox (Dropbox Inc. ) F n 15 GB free Referals, buy a device, exempt music 27

Online Storage n Also compared based on (as of 5/12) u u Search – can file content be basis F Dropbox only scans file names F One. Drive supports content scan for MS formats (Word, Excel, PP, etc. ) F Google supports many formats, even uses OCR for scanned content Others access F With Google Drive, file is either view or edit F One. Drive lets you specify for each file/user F 28 Dropbox must set up a shared folder for edit Copyright 2012 by Janson Industries

Other Storage n Microfilm and Microfiche u u Film is reel to reel, fiche is small rectangle of plastic film Hold microscopic images Need separate devices to read and write Readers considered auxiliary devices not peripheral devices F u Extremely long lasting 100 -500 years F F Copyright 2012 by Janson Industries Don't need the CPU to access the storage medium Magnetic disk 5 -30 yrs Optical 10 -100 yrs 29

Other Storage n n Enterprise storage - vast amount of capacity Storage array u u Separate device comprised of hundreds of disks Have multiple processors Act as "storage servers" Capacities up to. 5 PB (half a quadrillion bytes) 30 Copyright 2012 by Janson Industries

Other Storage n Solid state hard drive (SSD) u u u n Often used in combination with magnetic disk u Copyright 2012 by Janson Industries Uses non-volatile memory chips No moving parts Much faster than magnetic disk (up to 100 X) More expensive (up to 20 X) Limited number of writes (1 -5 mill) SSD acts as cache for frequently used files 31

Points to Remember n n n Secondary storage: non-volatile storage managed by a dedicated storage device Secondary storage serves as a source of input and target for output Wide variety of media measured by u u Speed Capacity Durability Read/write capability 32 Copyright 2012 by Janson Industries