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Information Technology
ITEC 1000
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Introduction to Information Technology ITEC 1000 – Winter 2010 – Peter Khaiter Lecture 11 – Computer Systems and Networks – Mar 22 System Performance Improvements - Multiple CPUs o Sharing memory and I/O facilities o Conflict among the CPUs for shared resources - Faster clock speed, buses and circuits o Improving technology to design faster CPU circuits and buses - Wider instruction and data paths o Wider interface between the CPU and memory allows to fetch more data in a single operation - Faster disk access o Smaller discs, more density packed, increased storage o RAID: data on different discs, multiple access simultaneously - More and faster memory o Reduces the time to access instructions and data Multiprocessing - Reasons o Increase the processing power of a system o Parallel processing - Types of multiprocessor systems o Tightly coupled systems o Loosely coupled systems 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 o Master-slave multiprocessing o Symmetrical multiprocessing (SMP) Master-Slave Multiprocessing - Master CPU o Manages the system o Controls all resources and scheduling o Assigns tasks to slave CPUs - Advantages o Simplicity o Protection of system and data - Disadvantages o Master CPU becomes a bottleneck o Reliability issues – if master CPU fails entire system fails Symmetrical Multiprocessing - Each CPU has equal access to resources - Each CPU determines what to run using a standard algorithm - Disadvantages o Resource conflicts – memory, i/o, etc. o Complex implementation - Advantages o High reliability o Fault tolerant support is straightforward o Balanced workload 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 o Fault-tolerant, scalable, well balanced, distance is not an issue - Two ways to configure o Shared-nothing model o Shared-disk model Shared-Nothing Model - High speed link between nodes - No sharing of resources - Partitioning of work through division of data - Advantage o Reduced communication between nodes - Disadvantage o Can result in inefficient division of work Shared-Disk Model - High speed link between nodes - Disk drives are shared between nodes - Advantage o Better load balancing - Disadvantage o Complex software required for transactional processing (lock, commit phases) Multi-Core Processors - Multi-core processor - two or more independent actual processors ("cores") - Each core can execute cpu instructions at the time (parallel computing) - Dual-core processor - two cores (e.g. Intel core duo) - Quad-core processor - four cores (e.g. Amd phenom ii x4 - Hexa-core processor - six cores (e.g. Amd phenom ii x6, intel core i7 extreme edition 980x) - Octa-core processor - eight cores (e.g. Amd fx-8150) - Coupling of cores: tightly or loosely Computer Interconnection - Communication channel – pathway for data movement between computers - Point-to-Point connectivity o Communication channel that passes data directly between two computers o Serial connection o Telephone modem o Terminal controller – handles multiple point-to-point connections for a host computer - Multipoint connectivity o Multidrop channel or shared communication channel Client-Server Architecture - Computer server provides services o File storage, databases, printing services, login services, web services - Client computers o Execute programs in its own memory o Access files either locally or can request files from a server Beowulf Clusters - Simple and highly configurable - Low cost - Networked o Computers connected to one another by a private Ethernet network o Connection to an external network is through a single gateway computer - Configuration o COTS – Commodity-off-the-shelf components such as inexpensive computers o Blade components – computers mounted on a motherboard that are plugged into connectors on a rack o Either shared-disk or shared-nothing model LAN Topology - Arrangement of workstations in a shared medium environment - Logical arrangement (data flow) - Physical arrangement (cabling scheme) LAN
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