Modern Computer Systems: Tightly Coupled and Loosely Coupled Multiprocessor Architectures

1. Chapter 11Modern 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

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 • 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 • 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