Client/Server Architecture

1
Client/Server Architecture

• Client/Server is advanced form of Distributed
• It is a way of looking at infrastructure
• let the best processor do the job
• PCs excel at ...
• Host systems excel at
• So take an activity and let them share it
• Database Server
• PC makes query, server retrieves data
• Mail Server
• PC creates mail, mail server routs it
• Web Server
• Server has web page, PC displays it

2
2-Tier vs. 3 Tier Architecture

• Client-Server is 2 tier
• Applications are split up
• part of software on client
• part of software on server
• Database is on server
• Problems
• when client s/w is updated
• as volume grows
• 3 Tier Architecture
• Separate platforms for three different functions
• input, process and storage

3
Three-Tier (or n-tier) architecture

• Front-End (Input - what users see)
• PCs or Thin Clients w/ GUI
• Windows or Web-based Interface
• Give access to middle tier, display what middle
  tier says
• Middle Tier (Processing)
• Application/transaction server(s)
• Does authentication processing
• Back-End (Storage)
• Database server(s) SANs
• Other possible layers
• Legacy System(s) - old centralized apps
• Load balancers

4
E-Commerce Models (pure plays)

• Pure-play vs. Clicks-and-Mortar
• Virtual Storefront pseudo store
• Online Marketplace or Electronic Broker
• Where buyers and sellers meet, auctions
• Information Broker
• Provides/sells info on firms, revenue from firms
• Transaction Broker
• Process online sales for other firms (fee based)
• Content Provider (syndicator)
• Packages news, music over the web
• Online Service Provider
• Access to internet portal to other services
• May sell member info
• Virtual Community
• Hosts chats, bulletin boards, etc.

5
IT Fundamentals

• 1. Total Cost of Ownership
• 2. How Computers Work
• 3. Organizational Computing
• 4. Storage
• 5. Input/Output
• 6. Buying a Desktop Tutorial

6
Total Cost of Ownership

• Hardware Acquisition - purchase price
• Software Acquisition - license or s/w
• Installation
• Training
• Support
• Maintenance - cost to upgrade, repair
• Infrastructure - link to nets, storage
• Downtime - lost productivity
• Space and Energy - utilities, facilities

7
TCO Takehome Project

• Research a Basic Unit and some upgrades (see next
  slide)
• Online from 2 sources
• Dell, Gateway, HP, Sony, Toshiba, IBM
• BestBuy, CompUSA, CircuitCity
• Find 2 systems that meet the specs (next slide)
• From different manufacturers
• Determine the cost of basic unit
• Determine cost if upgraded RAM, Hard Drive
  Monitor
• Identify the warranty and extensions
• Identify the service options and cost
• Determine total cost of ownership per PC
• (see other slide)
• Give me a memo describing systems and your
  recommendation - which computer and why

8
Basic Unit and Upgrades

• Basic Unit (Desktop)
• CPU - 2 gigahertz
• Hard Drive - 40 gigabytes
• RAM - 256 megabytes
• Portable storage - CD-R/RW DVD player
• Monitor - 17 inch CRT
• Upgrades
• CPU - 3 gigahertz
• RAM - 512 megabytes
• CD-R/RW DVD-R/RW
• Monitor - 17 inch flat screen (not flat panel)

9
Other TCO issues

1. We will want 30 units 2 backups
2. 5 units need on-site service, the others will be
   shipped for repair
3. Should either come with XP pro or we will want to
   add it (use their price)
4. We have MS Office licenses (65/PC)
5. We have other licenses (150/PC)
6. A part-time support person will be hired
   (10,000/yr, no benefits)

10
Data Representation Vol/Speed

• Computer devices are built using switches
• Switches have two possible states - ON or OFF
• Inside the computer
• circuit open 0 or OFF, circuit closed 1 or ON
• direction of current - one way is OFF, other is
  ON
• Each switch is a BIT - value of a bit is 1 or 0
• When you press a key on the keyboard
• a set of 0s and 1s are sent to CPU (ASCII code)
• ex 10011001 Y
• each character on keyboard 1 byte (8 bit code)
• 1Gbyte more than a billion characters
• Speed of Computer
• Hertz how fast things move (ex MegaHrtz)
• IPS (instructions per second, MIPS) how much
  can do
• FLOPS (floating pt ops) calcs w/ decimal pts.

11
What a CPU Does
Memory
12
What a CPU Does
Data Bus
Memory
External Bus or I/O Bus or Local/Expansion Bus
Internal Bus
13
Typical Steps

• What happens when you double-click on WP?
• What happens as you type your report?
• What happens when you save your report?
• What happens when you turn off PC?
• What happens when you open the file again?

14
What a CPU Does
Memory
disk cache
CPU
external cache
internal cache
DMA hard drive
disk controller
Sound card Video card
15
Computer Platforms

• High End
• Supercomputers (cutting edge)
• Parallel computing or super-cooled
• Used in labs or high-end networking
• Mainframe (business workhorse)
• Massive memory/processing
• Mid-range
• Super-minis
• Midrange server (dept wrkhorse)
• Network Server (souped up PC for Lan)
• Low-end
• Workstation
• Desktop
• Handhelds

16
Parallel Processing

• Slave Processors
• add-on processors are not really parallel, CPU
  still in control
• Fault Tolerant Processors
• where multiple processors mirror each other
• same transaction processed multiple times
• True Parallel Processors
• multiple CPUs
• either share memory
• or are virtual machines

17
Primary Storage (fast to slow)

• Internal Cache Memory (L1 - inside CPU chip)
• very fast volatile memory
• stockpile data/instructions CPU uses next
• External Cache Memory (L2 - outside CPU)
• fast volatile memory
• stockpile data/instructions for intl cache
• RAM - Random Access Memory
• volatile memory
• holds what might be needed by CPU
• generally expandable
• Triple cache (L1/L2 in CPU, L3 outside)

18
Secondary Storage Concepts

• Memory vs Secondary Storage
• Memory primary or working storage
• Writing vs. reading (output vs. input)
• Removable vs. non-removable
• whether medium is portable
• Media (disk) vs. Drive
• Media is the thing that is read
• Drive does locating(access)/reading/writing
• it also includes the drive controller (processor)
• Backup
• making a copy in case of disaster
• Archiving
• Older records stored on slower media

19
Secondary Storage Features

• No matter what technology used, there are
  features that never change
• Format - sequential/direct
• Capacity (volume of storage)
• Size (of device/media)
• Access time - how fast can locate
• Read time - how quickly read
• Ability to write/rewrite ( speed)
• Portability of device/media
• Fragility
• Longevity
• Cost of device/media

20
Magnetic Storage Devices

• Floppy Disks (thin plastic iron oxide)
• slow speed, low capacity
• Zip Disk/EZFlyer
• cassette larger than floppy, 250mb
• Hard Disk (thick platter rust)
• vacuum sealed, high volume, non-removable
• one platter or multiple platters stacked
• Removable hard disks
• Jaz/Orb (portable media)
• semi-portable (swappable but fragile)
• Tape Drives Tape media
• large reels, smaller cartridges

21
Optical Storage

• Laser beams read/write to plastic disk
• create pits to represent 1 or on
• higher capacity than magnetic
• Compact Disc Standard
• CD-ROM - read only
• CD-R - Write Once, Read Many
• CD-RW - erasable
• phase change - heat plastic, removes pits
• DVD - film industry standard
• DVD-ROM, DVD-RAM
• High capacity, two-sided

22
Memory Tech as Sec Storage

• EEPROM
• Electronically Erasable Programmable Memory
• Originally developed to control machines in
  factories
• Today use for secondary storage
• Flash drives
• Memory Sticks
• Memory cards
• Inside IPODs, MP3 players

23
Storage in Organizations

• Mass Storage Subsystems
• Racks of
• Large capacity tape cassettes
• Large capacity diskettes in sealed cases
• Robotic Arm that finds them
• CD Jukeboxes or Magazines
• RAID - Redundant Arrays of Inexpensive Discs

24
Enterprise Storage Architectures

• Local Storage
• Each server is connected to its own RAID
• Network Attached Storage
• RAID is attached to network so all servers can
  use it
• typically NAS work at the file level
• easy way to deal with growing storage needs
• good when a lot of devices need common files
• Storage Area Network
• Create a separate network of RAID devices that
  can communicate with your server network
  (subnetwork)
• good way to ease the load on your primary network
• typically SAN work at the sub-file level
• better for e-commerce (transaction data)
• Web Storage you use web to store stuff on
  vendor multiuser machine (server)

25
Storage Issues

• Everyday storage
• Pick storage that fits
• Security policies
• Backup issues
• What technology
• Backup policies
• When - how often
• What - which data?
• Where - how many media, reuse
• Archiving issues
• Infrastructure issues
• Centralized, decentral, distrib

26
Features of Input/Output

• Input human understandable data turned into
  machine readable form (digitize)
• Output machine readable data turned into human
  readable form
• Importance of dots in I/O
• We often use dots (pixels) to store characters or
  images
• Resolution -- as the number of dots increases,
  the better the image
• Importance of sampling in I/O
• Continuous reality (video,sound)
• Sample snapshot

27
Input devices

• Purpose to translate incoming data into machine
  readable form (digitize)
• Keyboard - translate keystroke to byte
• Pointing devices - translate movement or pressure
  to bits
• Graphic input - scanners
• Audio Input - sounds to bits
• microphones -- record only
• voice-input devices -- interpret
• Video Input - images to bits
• Scanner - creates a map of dark/light dots
• Digital Cameras - digitizes snapshot of reality

28
Output Devices

• Video - translate bits to images for display
• Monitors (Screen)
• CRT, CRT Flat screen, LCD Flat panel
• Electron gun, gas plasma, crystals
• Hard copy - translate bits to characters or
  pictures on paper
• Printers
• ink-jet vs. laser
• Audio - translate bits to sound
• Speakers
• Headsets

29
Input in Organizations

• Different from home because
• Biggest problem - human beings

30
Input Devices in Organizations

• Input to aid humans
• graphics tablet used with stylus
• head/eye position trackers
• touch screens
• voice-input
• Input to replace humans
• OCR (optical character recognition)
• Optical Codes -- ex bar code
• MICR (magnetic ink character recognition)
• Magnetic stripe technology (ex credit card)
• Smart Cards
• Intelligent Scanners
• Handwriting Recognition Devices

31
Output in Organizations

• Display
• larger monitors for desktop
• wall displays, flat panel screens
• projectors
• Printers
• Fast/High Volume laser Printers
• Color Laser
• Impact printers
• Dot-Matrix
• Line printers
• Thermal Printers
• Plotters

32
Output in Organizations (contd)

• Audio
• voice synthesizers
• prerecorded voice
• Video
• CD-ROM burners
• microfilm/microfiche
• archival storage

33
Hardware Features and Issues

• CPU
• Memory
• Secondary Storage
• Policies
• Technology
• Input devices and organizations
• Output
• Printers
• Monitors
• Audio/Video

34
Help When Buying a PC
35
Chip comparisons

• Intel (Celeron, PentiumIII, Pentium 4)
• Pentium 4
• clock (1.4 - 2.8Ghz), 512 L2 (half speed)
• 5.33 or 4 Ghz bus to memory
• Pentium III
• clock (850Mhz - 1.8), 512 L2, 1 or 1.33 Ghz bus
• Celeron (value chipset)
• Pentium chip 128 L2 (full sped)
• comparable bus
• AMD (Duron Athlon Athlon XP)
• double L1, same or double L2 (full speed)
• similar clock speed

36
Todays Memory

• SIMM, DIMM
• bank of memory chips on a circuit board
• Dynamic RAM (constant refreshing)
• DRAM -- pipelined
• S-DRAM - synchronized DRAM
• DDR S-DRAM - dual channel (tick/tock)
• R-DRAM (rambus) - memory processor
• Static RAM (less refreshing needed)
• costs more, use in cache

37
Add-On Recommendations

• Video Card or Graphics Accelerator
• get AGP bus, AGP slot and AGP card
• AGP Advanced graphics port standard
• memory (gt8 mb of DRAM or VRAM)
• MPEG (motion picture std)
• 3D engine
• Sound Card
• sampling rate -- higher the better
• Wavetable vs. FM synthesis
• is sound of instrument recorded or synthesized?
• MIDI (music standard)

38
Bus Standards May Need

• Universal Serial Bus (USB) and Firewire
• Still one character at a time but has a smarter
  processor
• Port can handle multiple devices
• Daisy Chain
• USB Hub
• Use with USB devices (ex flash drive)
• Other specialized buses
• AGP (graphics),
• Hard disk (SCSI, IDE),
• Music (MIDI),
• Network (T-connector or IRDA for infrared
  wireless)

39
Secondary Storage Issues

• Disk Controllers
• Some controllers let you attach more drives than
  others
• IDE(ATAPI) -- 2 drives max, slow (5400 or 7200
  RPM)
• bus speed up to 100mhtz
• SCSI -- 7 drives, faster (10k RPM)
• SCSI Ultra -- gt 14 drives, fastest
• For home use IDE is fine
• Photographic CD stds
• Kodak Photo CD series
• Flash PIX

40
Screen Issues

• Size of Screen
• VIS -- viewable area (15)
• Quality of Picture
• Dot Pitch -- space between dots
• .25 or smaller
• Non-interlaced less flicker
• Refresh Rate -- 75 hz or better
• Standard SVGA

41
Guidelines

• CPU -- older one ok
• especially if has cache (synch, full-speed?)
• Monitor --
• spend less now, upgrade later OR
• Buy high, use w/ new PCs later
• Hard Drive --
• get a moderately large one because
• can add more later (hard drive)
• ask about number of IDE and SCSI controllers

42
Guidelines (contd)

• Memory --
• leave room to expand
• considerations
• degree to which use multimedia
• volume of software, files you will have
• degree you use the internet
• windows environment (XP 128mb minimum)
• Expansion
• bays (how many unused doors on box?)
• expansion slots (how many unused?)
• power supply (200 watt or better)
• may need more power from wall socket