关注数据中心的能源效率,ISO/IEC 30134,正确的使用PUE值

简介

英文版本请点击链接https://newwitblog.wordpress.com/2016/06/10/data-center-resource-efficiency-pue-isoiec-30134/

自从绿色网格(The Green Grid)在2006年发布能源效率值Power Utilization Effectiveness (“PUE”),已经在数据中心行业及以外使用为数据中心能源使用效率的衡量指标. 是数据中心的在累计十二个月的所有能耗与IT负载使用的能源之比。绿色网格推广PUE的原意是让数据中心业主先探测然后制定减能耗计划来降低PUE值。

PUE虽然简单易懂,但是不正确的使用会带来困扰甚至于误导。不使用完整的12个月测量期或选择PUE1测量点的低于1.5的PUE值都是不正确做法的例子。

数据中心业内把低PUE值这个单纯的数据中心能源效率管理工具拿来与其他数据中心互相对比也是错误的使用PUE。模糊化的PUE值其实降低了PUE值的可信度。

绿色网格在发现这个错误使用PUE工具的现象之后发布一系列的报告,指导正确的PUE值的测量点,使用法,和深化PUE的相关术语。

国际标准化组织(The International Standards Organization – ISO)在2014年成立专门对数据中心能源使用关键绩效指标标准的ISO/IEC JTC 1/SC 39标准制定小组,绿色网格组织以观察者身份积极参与,提供了PUE和相关资料。
2016年4月份,ISO发布了数据中心能源使用关键绩效指标标准(ISO/IEC 30134)的三份子标准:

  • ISO/IEC 30134-1    第一部, ISO/IEC 30134 概述
  • ISO/IEC 30134-2    第二部, Power Usage Effectiveness (“PUE”) 能源使用效率
  • ISO/IEC 30134-3.    第三部, Renewable Energy Factor (“REF”) 再生能源因素

ISO 网店可买到以上正式标准文件。

ISO/IEC JTC 1/SC 39标准制定小组正在讨论并且计划推出另外两部子标准,这两部标准将是 IT设备能源效率(IT Equipment Energy Efficiency for Servers – ITEE) 和IT服务器使用效率(IT Equipment for Utilization of Servers – ITEU_SV).

 

重点考虑

既然PUE已经成为ISO标准,那么所有PUE值的采集以及计算就必须是符合标准(ISO 30134-2),比如IT负载必须是最接近IT设备的机柜内电源分配插座。

几乎所有的数据中心宣传资料所写的PUE值都不标明PUE分类或是否只是设计PUE(dPUE)。ISO/IEC 30134-2里指导PUE2是从数据中心列头柜或者房间式配电柜取得IT设备用电量。最精确的做法是从IT机柜内电源分配插座取得IT设备用电量,也就是PUE3的计算方法。ISO/IEC 30134-2也做出指导,PUE值在1.2-1.5之间,可以是用PUE2的采集方法,而PUE值在1.2(含)以下则必须是PUE3的采集方法。

ISO/IEC 30134-2也包含了延伸的PUE值,包括设计PUE(designed – dPUE),局部PUE(partial – pPUE),中期PUE(interim – iPUE)。

数据中心的PUE值也不是数据中心客户唯一关注的点,一个经常被忽悠但是很重要因素是供电和制冷系统的可用性及冗余,包括在设计期间以及运维中的调整对PUE值的影响,这个因素在ISO/IEC 30134-2的附录A里面有介绍。举个例子,如果在同一座城市里有两个数据中心A和B,A提供的PUE2值是1.4,B提供1.5,在不完全了解数据中心的总IT使用率,设计及运维而认为数据中心A比B的能耗低是不正确的。比如数据中心B可能把一直都把备用的一台制冷水机组并入N,也就是说N+1台的制冷水机组总是在运行状态,而数据中心A是N台制冷水机组是在运行状态,那么B把规避制冷水机组故障造成制冷量下降的风险看得比降低能耗是无可厚非的。又如果说数据中心A的2N UPS都是在节能(Economy)旁路市电状态而数据中心B应客户要求把2N UPS设置为标准状态,那么数据中心B的能耗较高但是新客户可以要求设置为节能模式的话,就能降低PUE值。

 

PUE已是标准工具

PUE是一个工具,而数据中心的能源管理及关键绩效指标及其他工具都能帮助我们对数据中心的资源(电,水,再生能源,IT设备使用率等等)管理。

选址,设计,选择设备,运维,采购IT设备等节点都影响数据中心的能源使用,就得把能耗放在这些节点的主要考虑因素之一。

以PUE为宣传目的,到底是PUE1/PUE2/PUE3/dPUE的模糊性,或者单纯把PUE值拿来比较两家数据中心而不考虑所有可以影响PUE值得因素,都对数据中心行业的健康发展无帮助。

有了划一的标准- ISO/IEC 30134,正确的使用标准来测量以及计算PUE及其他数据中心的关键指标将关注点聚焦在制定数据中心长期能效改善计划。关注,正确使用,参与数据中心能源效率或其他关键绩效指标 的制定,甚至试用并对相关主导机构提出加强及改善这些工具的意见将意义深远。

最终,重复一句,PUE是有用的,用得恰当,帮助自己的数据中心减低能耗是PUE工具的主要功能,宣传PUE值请写明PUE分类或者延伸的PUE值的全名。

关注数据中心的能源效率,ISO/IEC 30134,正确的使用PUE值

On Data Center Resource Efficiency, use of PUE and ISO/IEC 30134

The Green Grid released the definition and measurement of Power Utilization Effectiveness (“PUE”) in 2006 and its popularity has picked up with increased focus by all stakeholders on resource utilization efficiency. It is essentially an efficiency measurement, basically taking the total facility power usage divide by the total IT equipment power utilization over a period of 12 months, meant for use by a facility’s operator/owner to measure the energy efficiency of that particular facility which then can devise plan to improve its energy efficiency.

With the ease of understanding of PUE and its adoption came many different ways of measurement including using instantaneous and non 12 months measurement period and measurement points for the energy consumption on the IT side. The use by facility operators and large data center users have also promoted the use of low PUE to make non data center industry people to use PUE beyond its intended purpose of energy efficiency tool and more as a comparison metric.

Fortunately, The Green Grid has responded with a series of articles and whitepapers and continued to push for use of PUE in a proper and responsible manner.

The International Standards Organization has organized a standards committee comprising of more than a dozen countries under the name ISO/IEC JTC 1/SC 39, and The Green Grid has contributed its PUE work to it.

In April 2016, ISO has published three parts of data centers energy efficiency KPI series.

  • ISO/IEC 30134-1    Part 1 of the series which is overview of the entire ISO/IEC 30134 series
  • ISO/IEC 30134-2    Part 2, Power Usage Effectiveness (“PUE”)
  • ISO/IEC 30134-3.    Part 3, Renewable Energy Factor (“REF”)

You can get a copy of the above standards via ISO shop.

There are additional standard under the same series such as the IT Equipment Energy Efficiency for Servers (ITEE), and IT Equipment for Utilization of Servers (ITEU_SV).

Important Points

The right ways of using PUE and its requisite measurement points are as close to the IT equipment as possible. Most of the quoted PUE figures on industry press and marketing material never stated the PUE category, whereby PUE category 2 is measured at the room level PDU while PUE category 3 is measured in the rack at the in-rack PDU. In addition, for PUE factor that is reported to be under 1.2, it has to be a PUE category 3 type of measurement point. The different categories of PUE are described in ISO/IEC 30134-2.

Furthermore, most of the PUE figures being thrown around are in fact designed PUE or should be denoted as dPUE. The various PUE derivatives including partial PUE (pPUE) and interim PUE (iPUE) are also described in the standard.

Another important factor to consider is that different design and redundancy design and implementation affects the PUE. There is an important note in the ISO/IEC 30134-1 Annex A under the A.2 Data Centre Availability Objectives that discussed this point.

Let me give an example, if there are two data center facilities close to one another, while DC-A reports a PUE category 2 figure of 1.4 and DC-B reports a PUE category 2 figure of 1.5 do not mean DC-A is more superior than DC-B in terms of energy efficiency measures. Besides the factor of actual IT equipment installed in each site and their power consumption, we need to look into the design and redundancy put in by each facility as each may be meant for a different type of client with different redundancy and operations requirements. DC-A may put all the standby chillers on purely standby while DC-B put one of the standby chiller on-line in order to overcome any duty chiller problem, which meant DC-B’s cooling infrastructure will use up more energy. Or DC-A uses 2N UPS with both on economy mode while DC-B uses 2N UPS with both on normal mode under client demand.

PUE as a tool

PUE is a tool and in times to come just one of the tool in a wider tool set to improve the resource usage efficiency of data center facility.

From site selection to design, to selection of equipment, to operational adjustments, to selection and operations of IT equipment; there are multiple ways to effect meaningful resource usage effectiveness.

With the ISO/IEC 30134-2 PUE standard, we should focus on using this and other relevant tools, to correctly measure and then devise plan for energy reduction in a continuous manner.

The ISO/IEC 30134 series will have other relevant data center resource utilization KPIs and so is the rest of the data center community including the Green Grid and other regional/international bodies, we should use it right, we could experiment and suggest improvement to the tools and we should be aware of its limitations such as using it to compare one facility to another without full understanding of the circumstances towards the PUE figures.

On Data Center Resource Efficiency, use of PUE and ISO/IEC 30134