【DKV】DCD每日观点：PUE仅仅是一个指标，本身不是目标

yi321yi 2019-11-14

展开全文

Halvor Bjerke是DigiPlex的首席运营官

由DCD中国授权DKV编译并发表于DeepKnowledge微信公众号。

作为一个评价指标，电能使用效率(PUE)具有不可否认的优点。自2007年引入以来，它提供了一种简单的方法来评价数据中心效率的进展。该参数是一个简单的数字，由数据中心的总能耗除以其IT设备的能耗，显示了制冷、供电和其他因素所占用的其他能源。

由于该指标简单可行，因此在整个行业中得到了长足的改进。从2007年到2018年，整个行业的平均PUE从2.5下降到1.58，这意味着能源损失减少了60%以上。

但几乎所有这些进步都是在前半期取得的。平均PUE在2013年已经是1.65，到2018年只下降了0.07。然而在2019年5月Uptime研究所发布最新数据时却上升了，目前该指数为1.67。那么，进展是否已经停滞，甚至开始逆转?从局外人的角度来看，仍然有大量的能源被“浪费”，并伴随着巨大的“碳成本”。

举手之劳

可惜的是，似乎已经取得了一些轻松的进展。例如冷热空气分离、免费冷却、变频风扇控制和电量分配等措施在早期提供了巨大的进步。如今，一切都取决于细节，并带来了新的风险。依赖新风系统使数据中心容易受到火灾等当地气候的影响;对UPS的妥协让需要对增加当地电网的可靠性。对于一个依赖于单个数据中心的客户来说，这种做法可能很难被接受，对他们来说，即使是一秒钟的停机也可能造成灾难性的损失。

因此，尽管效率仍然至关重要，除大型集群和超大规模数据中心外，继续专注于降低PUE可能会降低自身的收益。目前朝向混合解决办法的方向，也正在削弱PUE作为单一指标的效力。随着服务器迁移到云上，剩余服务器机房的PUE会增加，虽然总体能耗在下降，但被更少的服务器所割裂。这种向公共云的迁移似乎推动了2019年全球平均PUE的增长。

真正的问题是，PUE并没有真正反映出其他类型的效率提高，而这些效率提高在一个数据中心的业务环境状况中扮演着越来越重要的角色。以热回收为例，使用数据中心的IT设备产生的热量为家庭和企业提供热源，或通过热泵直接发电。它有可能大幅减少能源浪费，但所需的额外设备可以提高该中心的PUE评级。

当然，在现实世界中，客户很少基于单一因素做出决定。2018年12月，Supermicro发布的研究表明，59%的决策者认为PUE很重要。但是，令人吃惊的是，58%的人甚至不知道他们的数据中心的PUE。研究还发现，只有9%的人将能源效率，作为其策略的首要因素，安全性、连接性和使用性能都被视为同等的，甚至对决策的影响更大。然而，由于PUE影响到运营的许多其他方面，从成本到声誉，这个数字可能低估了效率对决策的实际影响。

对于数据中心和客户来说，效率始终是核心考虑因素——以减少成本和保护环境。随着审查的增加，关键是要保留一个多样的评价方法，而不是过度依赖某个单一的度量，应考虑更广泛的量度及影响，包括:

使用可再生能源。调查电力供应的来源，但理想的是使用一个绿色的可再生能源供应链，保证每千瓦电能消耗都是直接来自于可再生能源。

更好的设计。现代、模块化和灵活、专业的的设施效率更高，可以定制化，以满足精确的 KPI，以实现性能和效率。

专业。数据中心运营的商业和环境影响如此之大，需要由具有特定技能和知识的专门团队来管理，以便做出正确的决策。

更好的维护。这些专家团队将了解专业设备，并保持其在最佳水平上工作，从而节省资金并提高可持续性。

创新。在数据中心的世界里，没有什么是静止的。创新是持续的，每次升级都能提高效率，降低能源成本。确保您充分利用最佳创新，并是可持续发展持续进步的基础。

合作关系。每个客户，每个负载，都是不同的。对于一些冗余将是至关重要的，对于其他人来说，直接云连接——服务和灵活地适应不断变化的需求，有机会去提高创新能力。

任何指标都必须视为路标，而不是解决方案本身。盲目遵守任何单一措施都可能扭曲决策，最终阻碍这一重要领域的进展。随着监察力度的加大，数据中心运营商及其业务客户必须定期向自己，提出更深入的问题，以揭示解决方案的真正效率，而不是依赖于像PUE这样的单一“魔性”指标。

这种对效率的实际效果更广泛、更全面的看法将会拥有更好的商业、环境和声誉。

英文原文

Halvor Bjerke, DigiPlex

Halvor Bjerke is chief operating officer at DigiPlex

Further sustainability gains may be lost through a narrow focus on PUE

As a metric, Power Usage Efficiency - or PUE - has undeniable merits. Since its introduction in 2007, it has offered a simple way to chart progress in data center efficiency. The rating is a single figure, derived by dividing the data center’s total energy consumption by that of its IT equipment alone - revealing the excess taken up by cooling, secure power supply and other factors.

Being simple and seemingly transparent, use of the metric has led to a general improvement across the industry. Between 2007 and 2018, average PUE across the industry fell from 2.5 to 1.58, meaning that energy losses were reduced by more than 60 percent.

But almost all of this progress was made over the first half of the period. Average PUE was already at 1.65 in 2013, falling only 0.07 to 2018 - and then rising when the latest data was published by the Uptime Institute in May 2019. It currently stands at 1.67. So, has progress stalled - or even begun to reverse? From an outsider’s point of view there’s still an awful lot of energy ‘wasted’ with a huge ‘carbon cost’ associated with it.

Low hanging fruit

Worryingly, it seems the easy gains have already been made. Measures like hot/cold air separation, free air cooling and better control over fans and power distribution offered big jumps early on. Now everything lies in the detail - and presents new risks. Reliance on external air leaves the center vulnerable to local events like fires; compromising on UPSs places tremendous faith in the reliability of the local grid. That faith might be hard to share for a client reliant on a single data center, for whom even a second of outage could prove catastrophically expensive.

So, while efficiency remains vital, continuing to concentrate on driving down PUE for its own sake might offer diminishing returns to all but the largest colocations and hyperscale centers. Current moves towards hybrid solutions are also undermining the efficacy of PUE as a single indicator. As servers are moved to the cloud, the PUE of remaining server-halls increases because overall energy consumption, although falling, is divided by fewer servers. It is this migration to the public cloud that seems to have driven 2019’s global rise in average PUE.

The real issue is that PUE doesn’t truly reflect other kinds of efficiency gain, which form an increasingly important part of a center’s environmental profile. Take heat return, using heat produced by the IT equipment in the data center either to provide heating for homes and businesses, or via heat pumps to generate power directly, as an example. It has the potential to substantially decrease energy waste, but the additional equipment needed could increase the center’s PUE rating.

In the real world, of course, clients rarely make a decision based on a single factor. In December 2018, Supermicro published research suggesting that 59 percent of decision-makers considered power efficiency important. But, strikingly, 58 percent did not even know their data center’s PUE. The research also found that only nine percent made power efficiency the primary factor in their strategy with security, connectivity and performance all seen as equal if not greater influences on decision making. However, because efficiency impacts so many other aspects of operations, from cost to reputation, this figure likely underplays the real impact of efficiency on decision-making.

For both data centers and clients, efficiency must remain a central consideration - to reduce both costs and environmental footprint. As scrutiny mounts, the key is to retain a sophisticated approach, without over-relying on any single metric. A wider range of metrics and impacts should be considered, including:

Using renewable energy. Audit where electricity comes from, offsetting helps, but the ideal is an auditable energy supply chain that guarantees every kWh consumed has been directly generated from a renewable source.

Better design. Modern, modular and flexible, purpose-built facilities are much more efficient and can be set up to meet precise KPIs for performance and efficiency.

Expertise. The commercial and environmental impact of data center operations is so large they need to be managed by dedicated teams with the specific skills and knowledge to make good decisions.

Better maintenance. These expert teams will understand specialist equipment and keep it working at optimum levels saving money and increasing sustainability.

Innovation. Nothing stands still in the world of data centers. Innovation is ongoing, and each iteration offers enhancements to efficiency and reductions in carbon cost. Ensuring that you are capitalizing on the best innovations is fundamental to continued progress on sustainability.

Partnership. Every customer, every load, is different. For some redundancy will be critical, for others direct cloud connection - advising and flexibly adapting to changing needs can create opportunities to create new efficiencies.

Any metric must be seen as a signpost rather than the solution itself. Blind adherence to any single measure can distort decision-making and ultimately impede progress in this essential area. As scrutiny intensifies, rather than relying on a single ‘magic bullet’ metric like PUE, data center operators, and their customers in the business, must routinely challenge themselves with deeper questions that uncover the real efficiency of their solutions.

This wider, more comprehensive view of real progress on efficiency will lead drive better commercial, environmental and reputational outcomes.