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 • We will want 30 units & 2 backups • 5 units need on-site service, the others will be shipped for repair • Should either come with XP pro or we will want to add it (use their price) • We have MS Office licenses ($65/PC) • We have other licenses ($150/PC) • 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 0’s and 1’s 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. Input Devices CPU Output Devices Storage Devices What a CPU Does Memory

12. Input Devices CPU Storage Devices Output Devices 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. Input Devices Output Devices Storage Devices 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 (cont’d) • 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. Today’s 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 (>=8 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 -- > 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 (cont’d) • 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