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


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

11-11


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

11-12


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

11-13


Cluster Models

Chapter 11: Modern

11-14


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

11-15


Blade and Rack of Beowulf Cluster

Figure 11.9

Chapter 11: Modern

11-16


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

11-17


Example: Point-to-Point

Chapter 11: Modern

11-18


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

11-19


Client-Server Network

Chapter 11: Modern

11-20


LAN Topology
 Arrangement of workstations in a shared medium
environment
 Logical arrangement (data flow)
 Physical arrangement (cabling scheme)

Chapter 11: Modern

11-21


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

11-22

Bus LAN Diagram

Chapter 11: Modern

11-23


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

11-24


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