1. Chapter 11 Modern Computer Systems, Clusters, and Networks
The Architecture of Computer Hardware and Systems Software: An Information Technology Approach
3rd Edition, Irv Englander
John Wiley and Sons 2003
Wilson Wong, Bentley College
Linda Senne, Bentley College

2. Basic Personal Computer System
Chapter 11: Modern Computer Systems, Clusters, and Networks

3. Mainframe Computer System
Chapter 11: Modern Computer Systems, Clusters, and Networks

4. Major PC System Components
Chapter 11: Modern Computer Systems, Clusters, and Networks

5. System Performance Improvements
Multiple CPUs
Faster clock speed, buses and circuits
Wider instruction and data paths
Faster disk access
More and faster memory
Chapter 11: Modern Computer Systems, Clusters, and Networks

6. Multiprocessing Reasons Types of multiprocessor systems
Increase the processing power of a system
Parallel processing
Types of multiprocessor systems
Tightly coupled systems
Loosely coupled systems
Chapter 11: Modern Computer Systems, Clusters, and Networks

7. Tightly Coupled Systems
Also called multiprocessor systems
Identical access to programs, data, shared memory, I/O, etc.
Easily extends multi-tasking, and redundant program execution
Two ways to configure
Master-slave multiprocessing
Symmetrical multiprocessing (SMP)
Chapter 11: Modern Computer Systems, Clusters, and Networks

8. Tightly Coupled Systems
Chapter 11: Modern Computer Systems, Clusters, and Networks

9. Master-Slave Multiprocessing
Master CPU
Manages the system
Controls all resources and scheduling
Assigns tasks to slave CPUs
Advantages
Simplicity
Protection of system and data
Disadvantages
Master CPU becomes a bottleneck
Reliability issues – if master CPU fails entire system fails
Chapter 11: Modern Computer Systems, Clusters, and Networks

10. Symmetrical Multiprocessing
Each CPU has equal access to resources
Each CPU determines what to run using a standard algorithm
Disadvantages
Resource conflicts – memory, i/o, etc.
Complex implementation
Advantages
High reliability
Fault tolerant support is straightforward
Balanced workload
Chapter 11: Modern Computer Systems, Clusters, and Networks

11. Loosely Coupled Systems
Clusters or multi-computer systems
Each system has its own CPU, memory, and I/O facilities
Each system is known as a node of the cluster
Advantages
Fault-tolerant, scalable, well balanced, distance is not an issue
Two ways to configure
Shared-nothing model
Shared-disk model
Chapter 11: Modern Computer Systems, Clusters, and Networks

12. Shared-Nothing Model High speed link between nodes
No sharing of resources
Partitioning of work through division of data
Advantage
Reduced communication between nodes
Disadvantage
Can result in inefficient division of work
Chapter 11: Modern Computer Systems, Clusters, and Networks

13. Shared-Disk Model High speed link between nodes
Disk drives are shared between nodes
Advantage
Better load balancing
Disadvantage
Complex software required for transactional processing (lock, commit phases)
Chapter 11: Modern Computer Systems, Clusters, and Networks

14. Cluster Models
Chapter 11: Modern Computer Systems, Clusters, and Networks

15. Beowulf Clusters Simple and highly configurable Low cost Networked
Computers connected to one another by a private Ethernet network
Connection to an external network is through a single gateway computer
Configuration
COTS – Commodity-off-the-shelf components such as inexpensive computers
Blade components – computers mounted on a motherboard that are plugged into connectors on a rack
Either shared-disk or shared-nothing model
Chapter 11: Modern Computer Systems, Clusters, and Networks

16. Blade and Rack of Beowulf Cluster
Figure 11.9
Chapter 11: Modern Computer Systems, Clusters, and Networks

17. Computer Interconnection
Communication channel – pathway for data movement between computers
Point-to-Point connectivity
Communication channel that passes data directly between two computers
Serial connection
Telephone modem
Terminal controller – handles multiple point-to-point connections for a host computer
Multipoint connectivity
Multidrop channel or shared communication channel
Chapter 11: Modern Computer Systems, Clusters, and Networks

18. Example: Point-to-Point
Chapter 11: Modern Computer Systems, Clusters, and Networks

19. Client-Server Architecture
Computer servers provides services
File storage, databases, printing services, login services, web services
Client computers
Execute programs in its own memory
Access files either locally or can request files from a server
Chapter 11: Modern Computer Systems, Clusters, and Networks

20. Client-Server Network
Chapter 11: Modern Computer Systems, Clusters, and Networks

21. LAN Topology
Arrangement of workstations in a shared medium environment
Logical arrangement (data flow)
Physical arrangement (cabling scheme)
Chapter 11: Modern Computer Systems, Clusters, and Networks

22. LAN Topologies: Bus Multipoint medium
Stations attach to linear medium (bus) using tap
Transmission from any stations travels entire medium (both directions)
Termination required at ends of bus to prevent the signal from bouncing
Break in cable brings down entire bus
Chapter 11: Modern Computer Systems, Clusters, and Networks

23. Bus LAN Diagram
Chapter 11: Modern Computer Systems, Clusters, and Networks

24. LAN Topologies: Tree Generalization of bus topology
Branching cable with no closed loops
Cable(s) begin at headend, travel to branches which may have branches of their own
Each transmission propagates through network, can be received by any station
Chapter 11: Modern Computer Systems, Clusters, and Networks

25. LAN Topologies: Ring
Repeaters are joined by unidirectional point-to-point links in a ring
As data circulates past a receiver, the receiver checks its address, and copies those intended for it into a local buffer
Data circulates until it returns to source, which removes it from network
Better performance at high levels of usage
Chapter 11: Modern Computer Systems, Clusters, and Networks

26. Ring LAN Diagram
Chapter 11: Modern Computer Systems, Clusters, and Networks

27. LAN Topologies: Star
Each station connected point-to-point to a central station, usually with two undirectional links
Switching in the central station connects pairs of nodes together
Central node can broadcast info, or can switch frames among stations
Failure of central station causes entire network to go down
Chapter 11: Modern Computer Systems, Clusters, and Networks

28. Star LAN Diagram
Chapter 11: Modern Computer Systems, Clusters, and Networks

29. Ethernet MAC Protocol MAC – Medium Access Control Ethernet and CSMA/CD
Carrier sense multiple access with collision detection
Four step procedure
If medium is idle, transmit
If medium is busy, listen until idle and then transmit
If collision is detected, cease transmitting
After a collision, wait a random amount of time before retransmitting
Chapter 11: Modern Computer Systems, Clusters, and Networks

30. Ethernet Frame
Chapter 11: Modern Computer Systems, Clusters, and Networks

31. Switched Ethernet
Chapter 11: Modern Computer Systems, Clusters, and Networks

32. Token Ring MAC Protocol
Token “seized” by changing a bit on the circulating frame to indicate start of frame rather than token
Default configuration requires sender to complete transmission and begin receiving transmitted frame before releasing the token
“Early token release” allows release of token after transmission but before receipt of frame
Chapter 11: Modern Computer Systems, Clusters, and Networks

33. Hubs The active central element of the star layout.
When a single station transmits, the hub repeats the signal on the outgoing line to each station.
Hubs can be cascaded in a hierarchical configuration
Ethernet hubs are physically a star but logically a bus.
Chapter 11: Modern Computer Systems, Clusters, and Networks

34. Bridges Allow connections between LANs and to WANs
Used between similar networks
Read all frames from each network
Accept frames from sender on one network that are addressed to a receiver on the other network
Retransmit frames from sender using MAC protocol for receiver
Chapter 11: Modern Computer Systems, Clusters, and Networks

35. Routers Similar to bridges but connect dissimilar networks
Convert format of the message to correspond to the protocol of the other network
Network traffic is specifically addressed to the router
Chapter 11: Modern Computer Systems, Clusters, and Networks

36. Wide Area Network Circuit switching Message switching Packet switching
Dedicated channel between source and destination for duration of connection
Message switching
Dedicated channel for an entire message
Packet switching
An independent path is created for each datagram
Virtual circuit switching
A route is created from source to destination before transmission begins and all datagrams are sent using the same route
Chapter 11: Modern Computer Systems, Clusters, and Networks

37. Networks vs. Clusters
Externally, clusters appear as a single computing unit.
Network nodes are individually identifiable.
Workload on a cluster is determined by cluster administration and load-balancing software.
Network workload cannot be controlled using the above method.
Chapter 11: Modern Computer Systems, Clusters, and Networks

38. High Performance Computing
Massively parallel processor architectures (MPP)
Clusters of power machines or larger Beowulf blade clusters
Well suited for problems that can be broken into subtasks
Grid computing
Supercomputer performance through distributing CPU processing to the spare CPU cycles of personal computers connected to a network
Chapter 11: Modern Computer Systems, Clusters, and Networks

39. Parallel Computers Massively parallel architectures
Hundreds to millions of CPUs
CPUs have small amounts of local memory
All CPUs have access to global shared memory
Pipelined CPUs
Results from one CPU flow to the next CPU for additional processing
Chapter 11: Modern Computer Systems, Clusters, and Networks

40. Copyright 2003 John Wiley & Sons
All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the permissions Department, John Wiley & Songs, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained herein.”
Chapter 11: Modern Computer Systems, Clusters, and Networks