ds

lec1

building and classifying parallel and distributed systems

bus-based multiprocessors
SMP:symmetric multi-processing
characterized by UMA:uniform memory access

cache: snoopy
not scalable

switched multiprocessors

crosspoint switches–expensive switching fabric

numa
non uniform memory access

distributed systems

• no shared clock

• no shared memory(use network interconnect)

• bus-based multicomputers

• switched multicomputers(any to any communication)

distribured software service models

multiprocessor/multicore os

network os
distribution is explicit

distributed os
奇葩

middleware

why building distributed systems

scalability
consideations:

• components(users,data,cpus):overloaded
• geography:communication latency,bandwidth,reliability
• administration:complexity

design issues

• reliability
  
  • availability: fraction of time system is usable
  • reliability: data must not get lost
• performance
  
  • communication network may be slow and/or unreliable

• scalability

  • distributable vs centralized alg

  service model

  centralized model
  limiting factor: cpus in system

client-server model
service client server

peer-to-peer model
equivalent capabilities
no machines dedicated to serving others

processor pool model
collection of cpus that can be assigned processes on demand

cloud computing model
software as a service
platform as a service:平台作为服务，由用户选择操作系统和中间软件，供应商提供硬件软件资源，来控制资源的使用
infrastructure as a service:基础设施作为服务，如何控制资源也交给用户

multi-tier client-server architecture