本章描述的特殊的云机制：
（1）自动伸缩监听器
（2）负载均衡器
（3）SLA监控器
（4）按使用付费监控器
（5）审计监控器
（6）故障转移系统
（7）虚拟机监控器
（8）资源集群
（9）多设备代理
（10）状态管理数据库
8.1自动伸缩监听器（automated scaling listener）
自动伸缩监听器机制是一个服务代理，它监控和追踪云服务用户和云服务之间的通信，用以动态自动伸缩。
The automated scaling listener mechanism is a service agent that monitors and tracks communications between cloud service consumers and cloud services for dynamic scaling purposes.
8.2负载均衡器（load balancer）
负载均衡器机制是一个运行时代理，其逻辑基本上就是基于水平扩展的思想。
The load balancer mechanism is a runtime agent with logic fundamentally based on this premise.
常见的水平扩展。
负载均衡器功能：
（1）非对称分配（asymmetric distribution）——较大的工作负载被送到具有较强处理能力的IT资源。
（2）负载优先级（workload prioritization）——负载根据其优先等级进行调动、排队、丢弃和分配。
（3）上下文感知的分配（content-aware distribution）——根据请求内容的指示把请求分配到不同的IT资源。
（4）劳动分工算法
8.3 SLA监控器（SLA monitor）
第九章重点描述
SLA监控器机制被用来专门观察云服务的运行时性能，确保他们履行了SLA中公布的约定QoS需求。
The SLA monitor mechanism is used to specifically observe the runtime performance of cloud services.
8.4按使用付费监控器（pay-per-use monitor）
按使用付费监控器机制按照预先定义好的定价参数测量基于云的IT资源使用，并生成使用日志用于计算费用。
按使用付费监控器收集的数据由计算付款费用的计费管理系统进行处理。
The data collected by the pay-per-use monitor is processed by a billing management system that calculates the payment fees.
典型监控变量：
（1）请求/响应消息数量
（2）传送的数据量
（3）带宽消耗
显示实现资源代理的按使用付费监控器，用来确定虚拟服务器的使用周期：
8.5 审计监控器
审计监控器机制用来收集网络和IT资源的审计记录数据，用以满足管理需要或者合同义务，有时这也是强制性要求。
The audit monitor mechanism is used to collect audit tracking data for networks and IT resources.
8.6故障转移系统（failover system）
故障转移系统机制通过使用现有的集群技术提供冗余的实现来增加IT资源的可靠性和可用性。
The failover system mechanism is used to increase the reliability and availability of IT resources by using established clustering technology to provide redundant implementations.
故障转移系统通常会被配置成只要当前活跃的IT资源不可用时，便自动切换到冗余或者待机的IT资源实例上。
有两种基本配置：
（1）主动——主动：IT资源的冗余实现会主动地同步服务工作负载。
（2）主动——被动：待机或非活跃的实现会被激活，从变得不可用的IT资源处接管处理工作，响应的工作负载就会被重定向到接管操作的这个实例上。
8.7虚拟机监控器（hypervisor）
虚拟机监控器机制是虚拟化基础设施的最基础部分，主要用来在物理服务器上生成虚拟服务器实例。
The hypervisor mechanism is a fundamental part of virtualization infrastructure that is primarily used to generate virtual server instances of a physical server.
虚拟机监控器通常限于一台物理服务器，因此只能创建那台服务器的虚拟映像。
虚拟机监控器只能把自己创建的虚拟服务器分配到位于同一底层物理服务器上的资源池里。
虚拟机监控器软件可以直接安装在裸机服务器上，提供对硬件资源使用控制、共享和调度功能。这些硬件资源包括：处理器、内存、I/O。
8.8资源集群（resource cluster）
资源集群机制是把多个IT资源实例分为一组，使得他们能够像一个IT资源那样进行操作。这增强了IT资源的组合计算能力、负载均衡能力和可用性。
The resource cluster mechanism increase the combined computing capacity, load balancing, and availability of the clustered IT resources.
常见的资源集群类型：
（1）服务器集群（service cluster）——物理或虚拟服务器组成集群以提高性能和可用性。
（2）数据库集群（database cluster）——这种高可用资源集群用于改进数据可用性，具有同步的特性，可以维持集群中使用到的各种存储设备上存储数据的一致性。
（3）大数据集集群（large dataset cluster）——实现了数据的分区和分布，这样目标数据集可以很有效地划分区域，而不需要破坏数据的完整性和计算的准确性。
资源集群的两种基本类型
（1）负载均衡的集群（load balanced cluster）——这种资源集群的专长在于在集群节点中分布工作负载。它通常要实现一个负载均衡器机制。
（2）HA集群（HA cluster）——它实现一个故障转移系统机制，监控失效情况，并自动将工作负载重定向为远离故障节点。
8.9多设备代理（multi-device broker）
多设备代理机制用来帮助运行时的数据转换，使得云服务能够被更广泛的云服务用户程序和设备所用。
The multi-device broker mechanism is used to facilitate runtime data transformation so as to make a cloud service accessible to a wider range of cloud service consumer programs and devices.
克服云服务和迥异的云服务用户之间的不兼容，创建映射逻辑来改变（或转换）运行时交换的信息。
多设备代理通常是作为网关（gateway）存在的，或者包含有网关组件。
可创建的转换逻辑层次包括：
（1）传输协议
（2）消息协议
（3）存储设备协议
（4）数据模式/数据模型
8.10状态管理数据库（state management database）
是一种存储设备，用来暂时地持久化软件程序的状态数据。
A state management database is a storage device that is used to temporarily persist state data for software programs.
状态管理数据库通常是由云服务使用的，特别是涉及长时间运行时活动的服务。
典型例题：
一、判断题
1、The automated scaling listener mechanism is a service agent that monitors and tracks communications between cloud service consumers and cloud services for static scaling purposes. （F ）
(The automated scaling listener mechanism is a service agent that monitors and tracks communications between cloud service consumers and cloud services for dynamic scaling purposes. )
2、The load balancer mechanism is a runtime agent with logic fundamentally based on this premise. （T ）
3The SLA monitor mechanism is used to specifically observe the runtime performance of cloud services. （T）
4、The data collected by the pay-per-use monitor is not processed by a billing management system that calculates the payment fees. （ F）
（The data collected by the pay-per-use monitor is processed by a billing management system that calculates the payment fees. ）
5The audit monitor mechanism is used to collect audit tracking data for networks and IT resources. （ T）
6、The failover system mechanism is used to decrease the reliability and availability of IT resources by using established clustering technology to provide redundant implementations. (F )
（The failover system mechanism is used to increase the reliability and availability of IT resources by using established clustering technology to provide redundant implementations. ）
7、The hypervisor mechanism is a fundamental part of virtualization infrastructure that is primarily used to generate physical server instances of a virtual server. ( F )
（The hypervisor mechanism is a fundamental part of virtualization infrastructure that is primarily used to generate virtual server instances of a physical server. ）
8、The resource cluster mechanism decreases the combined computing capacity, load balancing, and availability of the clustered IT resources. （ F ）
（The resource cluster mechanism increase the combined computing capacity, load balancing, and availability of the clustered IT resources. ）
9、The multi-device broker mechanism is used to facilitate runtime data transformation so as to make a cloud service accessible to a wider range of cloud service consumer programs and devices. ( T )
10、A state management database is a storage device that is used to permanently persist state data for software programs. （ F ）
（A state management database is a storage device that is used to temporarily persist state data for software programs. ）
二、选择题
1、The mechanism is a service agent that monitors and tracks communications between cloud service consumers and cloud services for dynamic scaling purposes.(B)
A、Resource cluster B 、 Automated scaling listener
B、C、Hypervisor D、Multi-device broker
2、which isn’t the Common resource cluster types :(C)
A、Server Cluster B、Database Cluster
C、backup cluster D、 Large Dataset Cluster
3、 A mechanism is a fundamental part of virtualization infrastructure that is primarily used to generate virtual server instances of a physical server.
A、Hypervisor B、Load Balancer
C、Audit Monitor D、SLA Monitor
4、 D mechanism is used to specifically observe the runtime performance of cloud services to ensure that they are fulfilling the contractual QoS requirements that are published in SLAs.
A、Audit Monitor B、Load Balancer
C、Hypervisor D、SLA Monitor
5、 B mechanism measures cloud-based IT resource usage in accordance with predefined pricing parameters and generates usage logs for fee calculations and billing purposes.
A、Audit Monitor B、 Pay-per-use monitor
C、Hypervisor D、SLA Monitor
6、 A mechanism is used to collect audit tracking data for networks and IT resources in support of (or dictated by) regulatory and contractual obligations.
A、 Audit Monitor B、Pay-per-use monitor
C、Audit monitor mechanism D、SLA Monitor
7、 B mechanism is used to increase the reliability and availability of IT resources by using established clustering technology to provide redundant implementations.
A、Audit Monitor B、Failover system
C、Hypervisor D、SLA Monitor
8、 A mechanism is used to group multiple IT resource instances so that they can be operated as a single IT resource.
A、Resource cluster B、Failover system
C、Hypervisor D、SLA Monitor
9、 D mechanism is used to facilitate runtime data transformation so as to make a cloud service accessible to a wider range of cloud service consumer programs and devices
A、Resource cluster B、Failover system
C、Hypervisor D、 Multi-device broker
10、 B provides a range of features for administering multiple hypervisors across physical servers.
A、 WEB B、VIM C、CPU D、ISP
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