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Capacity management is a process used to manage information technology (IT). Its primary goal is to ensure that IT resources are right-sized to meet current and future business requirements in a cost-effective manner. One common interpretation of capacity management is described in the ITIL framework. ITIL version 3 views capacity management as comprising three sub-processes: business capacity management, service capacity management, and component capacity management (known as resource capacity management in ITIL version 2). As the usage of IT services change and functionality evolves, the amount of central processing units (CPUs), memory and storage to a physical or virtual server etc. also changes. If it is possible to understand the demands being made currently, and how they will change over time, this approach proposes that capacity planning for IT service growth becomes easier and less reactive. If there are spikes in, for example, processing power at a particular time of the day, it proposes analyzing what is happening at that time and make changes to maximize the existing IT infrastructure, for example, tune the application, or move a batch cycle to a quieter period. This foresight from proactive capacity planning identifies: any potential capacity related issues likely to arise and justifies any necessary investment decisions to the business and IT stakeholders i.e. the precise server requirements to accommodate a future growth in IT resource demand, a technology refresh or a data center consolidation. These activities are intended to optimize performance and efficiency, and to plan for and justify financial investments. Capacity management is concerned with: * Monitoring the performance and throughput or load on a server, server farm, or property * Performance analysis of measurement data, including analysis of the impact of new releases on capacity * Performance tuning of activities to ensure the most efficient use of existing infrastructure * Understanding the demands on the service and future plans for workload growth (or shrinkage) * Influences on demand for computing resources * Capacity planning of storage, computer hardware, software and connection infrastructure resources required over some future period of time. Capacity management interacts with the discipline of Performance Engineering, both during the requirements and design activities of building a system, and when using performance monitoring as an input for managing capacity of deployed systems. == Factors affecting network performance == Not all networks are the same. As data is broken into component parts (often known frames, packets, or segments) for transmission, several factors can affect their delivery. *Delay: It can take a long time for a packet to be delivered across intervening networks. In reliable protocols where a receiver acknowledges delivery of each chunk of data, it is possible to measure this as round-trip time. *Packet loss: In some cases, intermediate devices in a network will lose packets. This may be due to errors, to overloading of the intermediate network, or to intentional discarding of traffic in order to enforce a particular service level. *Retransmission: When packets are lost in a reliable network, they are retransmitted. This incurs two delays: First, the delay from re-sending the data; and second, the delay resulting from waiting until the data is received in the correct order before forwarding it up the protocol stack. *Throughput: The amount of traffic a network can carry is measured as throughput, usually in terms such as kilobits per second. Throughput is analogous to the number of lanes on a highway, whereas latency is analogous to its speed limit. These factors, and others (such as the performance of the network signaling on the end nodes, compression, encryption, concurrency, and so on) all affect the effective performance of a network. In some cases, the network may not work at all; in others, it may be slow or unusable. And because applications run over these networks, application performance suffers. Various intelligent solutions are available to ensure that traffic over the network is effectively managed to optimize performance for all users. See Traffic Shaping 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Capacity management」の詳細全文を読む スポンサード リンク
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