Should Data Centers Be Kept Cool—Or Warm?
資料中心該保冷還是保暖？

Across the globe, data centers are stacked to the ceiling with shelf after shelf of humming servers. The collective number of operating CPUs is taking a toll on data centers’ energy bills, but the real culprit driving up the facilities’ energy costs may actually be their thermostats.
在全球範圍內，資料中心的天花板上堆滿了一架子又一架子嗡嗡作響的伺服器。大量運行的 CPU 正在對資料中心的能源帳單造成影響，但實際上，導致資料中心能源成本上升的真正罪魁禍首可能是它們的恆溫器。

Like humans, computers work best in a small temperature window roughly between 18 °C and 27 °C, with the sweet spot being about 24 °C. Data centers are on track to require an estimated 848 terawatt-hours by 2030, and up to 40 percent of that total will go toward cooling alone.
與人類一樣，電腦的最佳工作溫度大約在 18 °C到27 °C之間，最佳溫度約為24 °C。據估計，到 2030 年，資料中心將需要 848 太瓦時的電力，其中高達 40% 的電力將用於製冷。

Small improvements in energy consumption can be eked out by improving server operation efficiency. However, some experts believe that drastically changing how data centers are kept cool—or even, warm—may be the solution.
透過提高伺服器的運作效率，可以略微降低能耗。不過，一些專家認為，徹底改變資料中心的冷卻甚至保暖方式可能是解決之道。

A paper published on 18 October in Cell Reports Physical Science and another presented at the 2022 International Electron Devices Meeting conference present two very different visions: One in which data centers are kept at a sweat-inducing 41 °C, and another in which they’re cooled down to an inhospitable 100 kelvins (roughly -173 °C), respectively.
10月18日發表在《細胞報告物理科學》（Cell Reports Physical Science）上的一篇論文和在2022年國際電子器件會議（International Electron Devices Meeting）上發表的另一篇論文提出了兩種截然不同的設想：一種是將資料中心的溫度保持在讓人出汗的41 °C，另一種則是將資料中心的溫度降到令人難以忍受的100 kelvins（大約-173 °C）。

The Case for Cryogenic Cooling
低溫冷卻的理由

Arnout Beckers and Alexander Grill are coauthors on the cryogenic cooling paper. Beckers is an engineer and Grill is a researcher, both at Belgian nanoelectronics and digital technologies company Imec. They explain that cryogenically cooling a data center would not mean turning the whole building into an ice cube. Instead, the idea makes use of extremely cold and nonconductive liquids, like liquid nitrogen, to cool server systems by immersing them in the liquid.
Arnout Beckers 和 Alexander Grill 是低溫冷卻論文的共同作者。貝克斯是工程師，格里爾是研究員，兩人都在比利時奈米電子和數位技術公司 Imec 工作。他們解釋說，低溫冷卻資料中心並不意味著把整棟大樓變成冰塊。相反，這個想法是利用液態氮等極冷且不導電的液體，將伺服器系統浸入液體中進行冷卻。

“The main difference is in the cooling with liquids instead of air,” Beckers and Grill write in a joint email response. “Liquid-immersion cooling is already a trend coming to data centers, but with liquids above ambient temperature.”
"主要區別在於使用液體而不是空氣冷卻，"Beckers 和 Grill 在聯合電子郵件回覆中寫道。 "浸液冷卻已成為資料中心的趨勢，但使用的是高於環境溫度的液體"。

At these extremely cold temperatures, computing systems can see increases in efficiency as a result of reducing obstacles like mechanical resistance and transistor switching. Yet Beckers and Grill say that cooler isn’t always better. For example, cooling these classical servers down to the temperatures needed for quantum computers (1 kelvin or -272 °C) wouldn’t make the computers hyperefficient.
在這種極低的溫度下，由於減少了機械電阻和電晶體開關等障礙，計算系統的效率得以提高。然而，貝克斯和格里爾表示，低溫並不總是更好。例如，將這些經典伺服器冷卻到量子電腦所需的溫度（1開爾文或-272 °C）並不會使電腦效率過高。

By bringing servers’ temperatures down through cryogenic cooling, Beckers, Grill, and their coauthors argue that data centers could see a 16-fold increase in computational performance—partially offset by a 4-fold increase in the energy used to power the cooling system.
貝克斯、格里爾和他們的合作者認為，透過低溫冷卻降低伺服器的溫度，資料中心的運算效能可以提高16 倍，但冷卻系統的能耗卻增加了4 倍，這部分抵消了運算效能的提高。

“In a cold data center, most of the energy will go to the cooling, and only a small fraction will be for compute. The aim is to lower the compute energy as much as possible to maximize the net benefit,” Beckers and Grill write.
"在冷資料中心，大部分能源將用於冷卻，只有一小部分用於計算。我們的目標是盡可能降低計算能耗，使淨效益最大化，"Beckers 和 Grill 寫道。

The Case for Warm Data Centers
暖數據中心案例

Rakshith Saligram is a graduate student in electrical and computer engineering at the Georgia Institute of Technology whose research focuses on cryogenic computing. He says that while work toward cryogenic server cooling has gained traction in recent years, it still faces many practical challenges, including prohibitive costs to transform the cooling systems and the introduction of new points of failure in the systems.
拉克希思-薩利格拉姆（Rakshith Saligram）是佐治亞理工學院電子與電腦工程專業的研究生，他的研究重點是低溫計算。他說，雖然近年來低溫伺服器冷卻的工作取得了進展，但仍面臨許多實際挑戰，包括改造冷卻系統的成本過高，以及在系統中引入新的故障點。

With those challenges in mind, perhaps a warmer data center is the solution. This is the argument that Shengwei Wang, director of the Research Institute for Smart Energy at the Hong Kong Polytechnic University, and his coauthors make in their Cell Reports Physical Science paper on the global energy saving potential of warming up data centers.
考慮到這些挑戰，或許一個更溫暖的資料中心才是解決之道。這就是香港理工大學智慧能源研究所所長王勝偉和他的合作者在《細胞報告》物理科學論文中提出的論點：資料中心暖化具有全球節能潛力。

Wang and his colleagues evaluated ongoing research on raising the temperature of data centers and found that allowing temperatures to reach 41 °C could result in an energy savings of 56 percent globally. Unlike cryogenic cooling, which aims to reduce energy costs by improving compute efficiency, warm data centers would instead reduce energy costs by reducing the overall use of “chiller cooling,” such as air conditioning, in favor of “free cooling” from ambient external air.
Wang和他的同事評估了正在進行的有關提高資料中心溫度的研究，發現讓溫度達到41 °C可以在全球範圍內節省56%的能源。低溫冷卻的目的是透過提高運算效率來降低能源成本，而暖資料中心則不同，它將透過減少空調等"冷卻器冷卻"的整體使用，轉而使用外部環境空氣的"自由冷卻"來降低能源成本。

Essentially, raising the internal temperature of the data center creates a smaller difference between internal and external temperatures, and thus requires less active cooling to maintain the internal temperature.
從根本上說，提高資料中心的內部溫度可以縮小內部和外部的溫差，從而減少維持內部溫度所需的主動冷卻。

Even though servers have traditionally been kept cool, Wang says that advances in material and server technology mean this isn’t necessarily the case anymore. In their paper, Wang and his colleagues cite server-performance guidelines from the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) that already recommend operating temperatures up to 45 °C for newer classes of data processors.
儘管伺服器在傳統上一直保持低溫，但 Wang 說，材料和伺服器技術的進步意味著情況不一定是這樣了。在論文中，Wang 和他的同事引用了美國暖氣、冷氣和空調工程師協會（ASHRAE）的伺服器效能指南，該指南已經建議較新等級的資料處理器工作溫度最高可達 45 °C。

However, several things still need to go right for this warm data center future to come to fruition, such as the widespread proliferation of microprocessors and transistors that can handle warmer temperatures. Even then, these systems may face physical obstacles, says Benjamin Lee, a professor of electrical and systems engineering at the University of Pennsylvania who has previously written about data centers for IEEE Spectrum.
不過，要實現資料中心溫暖的未來，還需要做好幾件事，例如能夠承受較高溫度的微處理器和電晶體的廣泛普及。賓州大學電機與系統工程教授班傑明李（Benjamin Lee）曾為《IEEE Spectrum》撰寫過資料中心的文章，他表示，即便如此，這些系統仍可能面臨物理障礙。

“Microprocessors and their transistors could be designed to operate at higher temperatures, but their performance may suffer,” Lee says. “Current leakage increases with temperature, which means a microprocessor operating at higher temperatures will use more power to compute the same answer. Transistors could be tuned to control leakage better, but those solutions may harm transistor performance, causing the microprocessor to compute more slowly.”
"微處理器及其電晶體可以設計在更高的溫度下運行，但其性能可能會受到影響，"Lee 說。 "漏電流會隨溫度升高而增加，這意味著微處理器在更高溫度下工作時，計算相同的答案需要消耗更多的功率。可以對晶體管進行調整，以便更好地控制洩漏，但這些解決方案可能會損害電晶體的效能，導致微處理器的計算速度更慢。

Ultimately, Lee says that both warm and cryogenically cooled data centers could have their own benefits and downsides. The ultimate winner will come down to the balance of cost to performance as well as each data center’s threshold for risk.
最終，Lee 表示，溫冷資料中心和低溫冷卻資料中心各有利弊。最終的勝者將取決於成本與效能之間的平衡，以及每個資料中心的風險閾值。

“Warm data centers represent an incremental optimization and improvement beyond the current state of the art [while] cryogenic cooled data centers represent a more expensive, speculative solution,” Lee says. “Warm data centers reduce the costs of cooling without much impacting performance. Cryogenic data centers significantly increase the costs of cooling with the goal of improving performance by even more.”
"Lee說："暖資料中心代表了在現有技術水平上的逐步優化和改進，而低溫冷卻資料中心則代表了一種更昂貴的投機性解決方案。 "暖溫資料中心降低了冷卻成本，但對效能影響不大。低溫資料中心大大增加了冷卻成本，但目標是提高更多的效能。