Lec8chap7f04

Lecture 9 / Chapter 7 COSC1300/ITSC 1401/BCIS 1405 10/19/2004

F.Farahmand 1 / 11 File: lec8chap7f04.doc

General Items: ? H

Reading Materials: ? T

Miscellaneous:



Electronic Storage - The medium on which we can keep data, instructions, and

information - Examples: Floppy Disk, Tape, PC Card, etc. - Is monitor a storage device? - Storage Types: Primary, Secondary

Memory Devices - Temporarily hold the data - Used during processing - Two basic types: V? and N? - Also called primary storage

Storage - Known as the secondary storage, permanent storage, mass storage - It is nonvolatile - May have different media – physical materials to store the data - Examples: Floppy drive, Hard drive, Tape, etc. - Basic operations: Search, Read, Write - Basic properties:

o Access time: Time to locate the item (data) ? Order of msec

o Capacity: How much data can be stored ? In order of GB

o Technology and medium: Type of physical material used ? Floppy, Tape



What is the big idea?

-

Storage Devices

Primary Storage Secondary Storage

Volatile Nonvolatile FD CD

Tape DVD

HD

MEMORY PROCESSOR

STORAGE

WORK SPACE YOU

CABINET



Comparing Different Storage Media and Memory: - Speed (Access time) – Memory is faster - Capacity – Storage devices have more capacity - Cost – Memory is more expensive - Degradation:

Information lasts forever or five years-whichever comes first! Difference between DISC and DISK? - Disks (diskette) are any storage media which utilize electromagnetic

platters to store data. o Floppy disks, Hard disks

- Discs are storage media which use the patterns of light bouncing off a pitted surface to store data

o Compact discs, DVD discs So is it flying DISC or DISK?

Memory (RAM)

Compact Disc

Floppy Disk

Tape

Hard Disk



Floppy Disks - Uses magnetic storage medium – been around since invention of

PCs - Density

o Number of bits it can store o Low (720 KB), High Density (1.47 MB)

Is it 1.44 or 1.47 MB Floppy? - Evolution:

o 8-inch disk (1967) o 5.25 Floppy – 360 KB capacity, 1981 o 3.5 Disks – 1.47MB capacity

- Basic terminologies: Uses magnetic media (plastic disks) - Compatibility: Upward and downward compatible

o No upward compatible (can’t recognize the higher density) - Floppy Disk Drive (FDD) parts

o Shutter, Header, Motor o Basic operations: Search, Read, Write

- Storing capability: o There are 40 tracks per side of the recording surface o 18 sector per track o 512 bytes per sector o High density floppies have 2 sides

2 x 80 x 2 x 512 x 18 = 1,474,560 MB o 2-8 sectors make a Cluster o A file resides on one or more clusters



- Some related terminologies o Formatting: process of preparing the disk for R/W o Write-protection: Can’t write into the disk o Back-up: File duplication o Life time (5-7 years)

Hard Disks - Hard disk drives - Faster access time than floppies and have much higher capacity - Store data magnetically - Basic components:

o Platter: Coated glass, aluminum, or ceramic with materials that allows recording data

o Motor: Turns the platters (72000 rpm) o R/W Header: Mechanical moving head across the platter –

moving at 170 mph! o Controller (HDC): Interfaces the computer and the HD –

three basic types: - USB: Allowing daisy chain - EIDE: Commonly used, can support up to 4 drivers at a

speed of 66 MBps, variations include ATA, DMA, etc. - SCSI: Used for many other drivers including CD-ROM

drivers, printers – supports daisy chaining, operates at 160 MBps – other variations include SCSI-3, Ultra SCSI, etc.



Related terminologies:

o Partitioning: Virtually splitting the HD o Head Crash: the gap between the platter and the header is

blocked due to shocks or contamination - 2 millionths of an inch! How large is that? – Hair-proof!

o Disk Cache: Memory holding frequent data in use o Defragmenting: removing unused space on the HD o Internet Hard Driver: Data storage on remote servers

- Integrated hard disks: called RAID – Redundant Array of Independent Disks

o Used for backup and reliable storage o Can be based on 1:1 backup (mirroring) o The data can be split into multiple disks resulting in more

reliable and space efficient storage (striping)



Compact Disc (CD) - Also called optical disc (watch the spelling!) - Metal disc with a bout a 5-inch diameter and 1/12th of an inch

thickness - Stores data, etc. using microscopic notches (called pits)

o When the light hits the pit it returns indicating a logic 1 - Types: - Basic Operation:

o Consists of a spiral single track circling around the CD o The track is divided into evenly sized sectors o Pits and Bumps generate logic 1 and 0

So how small is a pit?

o The height of the bump is 125 nanometer - A nanometer is a billionth of a meter



o Storage capacity (sound and data) : o Let’s assume the CD can record 80 minutes of music, how many

bytes can it store? o 44,100 samples/channel/second x 2 bytes/sample x 2 channels x 80

minutes x 60 seconds/minute = 846,720,000 bytes about 1GB - Types:

o CD-ROM - Read-only memory, the contents can not be changes - Uses CD-ROM drive or player - 650MB to 1GB storage capacity (450 x more than a FD) - Data transfer rate: 150KBps per X – 48X = 7.2 MBps

o CD-R - Multi session recordable CD – not erasable - Writes at about 8X and reads at about 24X rate

o CD-RW - Rewriteable CD – Like a floppy - Writes at about 8X / Rewrites at about 10 X / Reads at

about 24X rate Tape - Magnetically coated ribbon which can store data - Uses tape cartridge - Uses Sequential access not Direct access

o Sequential access searches for data sequentially o Direct access (Random access)

- Accesses the data immediately - Remember RAM?



Digital versatile disc (DVD) o Very high capacity disc (4.7 – 17 GB) o Better quality than CDs

o Pits are packed closer together o Double layers of pits o Double sided

o Types: DVD+RW, DVD-ROM, DVD-R o How long is the track? 7.5 miles on each side!!!



Mobile Storage Devices - Moveable thin credit card-size storage devices - Come in different types depending on the thickness

Smart Cards - Moveable thin credit card-size storage devices - Basic types:

o Intelligent, and memory cards o Examples: Calling Card? License Card? E-money? o Are they secure?

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Devices & Hardware