The architecture of computer hardware and systems software an information technology approach ch11

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 Basic Personal Computer System Chapter 11: Modern 11-2 Mainframe Computer System Chapter 11: Modern 11-3 Major PC System Components Chapter 11: Modern 11-4 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 11-5 Multiprocessing  Reasons  Increase the processing power of a system  Parallel processing  Types of multiprocessor systems  Tightly coupled systems  Loosely coupled systems Chapter 11: Modern 11-6 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 11-7 Tightly Coupled Systems Chapter 11: Modern 11-8 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 11-9 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 11-10 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 11-25 Ring LAN Diagram Chapter 11: Modern 11-26 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 11-27 Star LAN Diagram Chapter 11: Modern 11-28 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 11-29 Ethernet Frame Chapter 11: Modern 11-30 Switched Ethernet Chapter 11: Modern 11-31 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 11-32 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 11-33 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 11-34 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 11-35 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 11-36 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 11-37 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 11-38 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 11-39 ... 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... 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,... 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