数据库应用与设计-大型数据库系统架构设计方法.pptVIP

Latency GOAL FOR REAL-TIME SYSTEMS 1 10 100 1000 10000 Jobs/second Low latency at given load 数据库应用与设计-大型数据库系统架构设计方法全文共144页，当前为第128页。 Latency 1000 100 GOAL FOR BATCH SYSTEMS 10000 10 1 Jobs/second High Jobs/sec at a reasonable latency 数据库应用与设计-大型数据库系统架构设计方法全文共144页，当前为第129页。 Latency(ms) 10 1 0 0.2 0.4 0.6 0.8 1 Load THE LATENCY CURVE 1000 100 Better load balancing strategies can dramatically improve both latency and throughput 数据库应用与设计-大型数据库系统架构设计方法全文共144页，当前为第130页。 LOAD BALANCING TENSIONS We want to reduce queue lengths in the system to yield better latency We want to lengthen queue lengths to keep a “buffer” of work to keep busy during irregular traffic and yield better throughput For distributed systems, equalizing queue lengths sounds good 数据库应用与设计-大型数据库系统架构设计方法全文共144页，当前为第131页。 INTRODUCTION ? ? Load Balancing is a technique to spread work between two or more computers, network links, CPUs, hard drives, or other resources, in order to get optimal resource utilization, maximize throughput, and minimize response time. Load balancer is a tool that directs a client to the least busy or most appropriate Web server among several servers that contain mirrored contents. 数据库应用与设计-大型数据库系统架构设计方法全文共144页，当前为第132页。 WHY IS LOAD BALANCING OF SERVERS NEEDED? ? ? ? The web server may not be able to handle high volumes of incoming traffic. The users will have to wait until the web server is free to process their requests. There may be a situation where upgrading the server hardware will no longer be cost effective. 数据库应用与设计-大型数据库系统架构设计方法全文共144页，当前为第133页。 LOAD-BALANCING TECHNIQUES ? Three types of load balancers exist: ? ? ? Hardware appliances Network switches Software 数据库应用与设计-大型数据库系统架构设计方法全文共144页，当前为第134页。 LOAD-BALANCING TECHNIQUES ? ? ? A hardware appliance-based load balancer is a closed box. A network switch-based load balancer uses a Layer2 or Layer3 switch to integrate