分布式资源管理.pptx

SLA-Driven Dynamic Resource Management for Multi-tier Web Applications in a CloudSLA-DrivenSLA：A service-level agreement (SLA) is a part of a service contract where the level of service is formally defined.Service level agreements are offered by service providers as a service based agreement rather than a customer based agreement. Multi-tier Web ApplicationsIn software engineering, multi-tier architecture is a client–server architecture .The presentation, the application processing, and the data management are separate processes.Layer vs Tier逻辑层（Layer）重视职责的划分，职责之间常常是上层使用下层的关系——但是根本不关心上层是否“能分布”在不同的机器上。物理层（Tier）指“能分布”在不同机器上的软件单元，不同物理层之间必须有跨机访问的能力——可以通过远程调用、或者通信协议等方式。Layer vs Tier按Tier分层：JAVA EEOutlines IntroductionSpecific objectiveMethodologyPreliminary investigations and experimentPreliminary resultsIntroduction : SLAMost cloud providers provide service-level agreements (SLAs) for availability or other quality attributes.The most important quality attribute for Web applications from the user’s point of view, response time, is not addressed by current SLAs.Introduction : response timeThe reason for this is obvious: Web application traffic is highly unpredictable, and response time depends on many factors.Response time had the ability to dynamically and automatically allocate additional resources to the application as traffic grows.Introduction : tierA typical Web application consists of three tiers: a Web server tier an application server tier a database server tierEvery tier may place a heavy demand on specific resources.Introduction : tierA Web server tier requires high network bandwidth to handle incoming traffic.An application server requires a large amount of CPU time.A database tier requires high disk throughput.IntroductionAbove all , the Web application depends on one or more of the other tiers.Therefore , whenever a tier becomes a bottleneck, the efficiency of dependent tiers also degraded the whole application’s performance starts decreasing drama