学习资料： ITIL培训基地专家讲堂直播 300期视频回放

引：可用性管理是确保IT服务交付达到业务目标，提供给客户满意的服务。
服务可用性，即要保证客户服务的可用性和可靠性，而可用性的指标有哪些呢？在细节上，网页的响应时间如何定？错误率如何定？是否基于不同的用户定不同的指标？故障生命周期与可用性计算是否按照V3的设计...

小编本期抛出的话题是：

可用性的指标如何定，才能满足客户的需求？

     你是如何做的，分享一下哦！

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懒得码字了，自己看Service Design那本书的4.4 Availability Management，重点看4.4.7 Key Performance Indicators，如下内容：

Manage availability（可用性） and reliability （可靠性）of IT service:
· Percentage reduction in the unavailability of services and components
· Percentage increase in the reliability of services and components
· Effective review and follow-up of all SLA, OLA and underpinning contract
breaches
· Percentage improvement in overall end-to-end availability of service
· Percentage reduction in the number and impact of service breaks
· Improvement in the MTBF (Mean Time Between Failures)
· Improvement in the MTBSI (Mean Time Between Systems Incidents)
· Reduction in the MTRS (Mean Time to Restore Service).

Satisfy business needs （满足业务需求）for access to IT services:
· Percentage reduction in the unavailability of services
· Percentage reduction of the cost of business overtime due to unavailable
IT
· Percentage reduction in critical time failures, e.g. specific business peak
and priority availability needs are planned for
· Percentage improvement in business and users satisfied with service (by
CSS results).

Availability of IT infrastructure achieved at optimum costs （最适宜的成本）:
· Percentage reduction in the cost of unavailability
· Percentage improvement in the Service Delivery costs
· Timely completion of regular Risk Analysis and system review
· Timely completion of regular cost-benefit analysis established for
infrastructure Component Failure Impact Analysis (CFIA)
· Percentage reduction in failures of third-party performance on
MTRS/MTBF against contract targets
· Reduced time taken to complete (or update) a Risk Analysis
· Reduced time taken to review system resilience
· Reduced time taken to complete an Availability Plan
· Timely production of management reports
· Percentage reduction in the incidence of operational reviews uncovering
security and reliability exposures in application designs.

标记中文的地方是关键点，即：在“满足业务需求”的前提下，以“最适宜的成本”来管理“可用性”和“可靠性”（以及可维护性maintainability和可服务性serviceability）。MTBF、MTBSI、MTRS等的计算方法书里有，自己看吧。KPI细节跟客户商定，牢记量化原则。不同客户需求，不同的KPI。

细节上的可用性真的不好度量，与其度量也不准确，不如别费这个功夫去度量

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