Reality Check on Liquid Cooling in the Data Center

December 9, 2013

Evaluating liquid cooling for a data center requires an understanding of both the technical approach and ability of the solution to address the business and operational concerns of the data center.

To be practical, it must not only be technically sound but must provide reduced operational costs (OpEx) and/or capital expenditures (CapEx) and must satisfy other metrics such as serviceability,  monitoring, redundancy, failure isolation and even server warranty coverage.

Approaches to Liquid Cooling

Nearly every data center is liquid cooled today.  Most data centers bring liquid into Computer Room Air Handlers (CRAH) or Computer Room Air Conditioning (CRAC) units to cool the air in the data center.  CRAH units bring chilled water in to cool the air. The refrigerant comes into CRAC units as a liquid.  It is not a question of should we liquid cool? It’s a question of how to liquid cool most efficiency?  How to get server heat into liquid to reduce energy costs, mitigate expansion costs and enable increased density?

There are three significant drawbacks with CRAC and CRAH units. The first is that to produce cold enough air to cool servers, the liquid coolant coming to the data center (facilities liquid) must be refrigerated to a temperature colder than ambient (outdoor) air. Chilling is expensive. The second is CRAC and CRAH units produce cold air at the periphery of the data center and considerable effort is needed to move it to the racks. Third, considerable effort is needed move it through the servers via server fans.

Rear door, in-row and over-row liquid coolers focus on reducing the cost of moving air about the data center by placing the air-cooling unit as closer to the servers. For example, Rear Door Coolers replace rear doors on the rack with a liquid cooled heat exchanger that transfers server heat into liquid as hot air leaves the servers. The servers are still air-cooled and facilities liquid must be brought into the computer room at the same temperatures as is needed for CRAH units, <65 degrees F and that liquid exits at <80 degrees F.  While air handling is simplified expensive chillers are still required and server fans still consume the same amount of energy.

“Direct Touch” cooling replaces air heat sinks with ‘Heat Risers’ which transfer heat to skin of server chassis where cold plates between servers transfer heat to refrigerant so the heat can be removed from the building. This eliminates fans in the server and the need to move air around the data center for server cooling.  However facilities are still needed to cool the refrigerant to <61°F and cold plates between the servers reduce the capacity of a 42U rack to ~35 RUs.

Immersion cooling uses an all liquid path to remove server heat by placing servers in tanks of dielectric fluid or filling custom servers with dielectric fluid.  Key concerns with this technology are the maintenance of servers, large quantities of oil-based coolant in the data center, modification of servers with non-stand parts and poor space utilization as in effect the “racks” are lying on their backs.

The most significant advancement in practical liquid cooling can be seen in Asetek’s RackCDU™ Direct-to-Chip (D2C™) hot water cooling system.

D2C hot water liquid cooling brings cooling liquid directly to the server components that generate the most heat within a server and cools the remaining components with air. This solution removes 60% to 80% of the heat generated by servers with an all-liquid path. Pumps replace fan energy in the data center and server, and hot water eliminates the need for chilling the coolant. The air-cooled side of the solution is also more efficient as lower volumes of warmer air are sufficient to cool the remaining components. D2C liquid cooling dramatically reduces chiller use, CRAH fan energy and server fan energy, delivers energy savings of up to 80% and server rack density increases of 2.5x-5x times compared to air-cooled data centers.

Addressing the Business and Operational Concerns of Data Centers

Cost Containment be it CapEx or OpEx is a necessity for data centers.  30+ Kw/racks enabled by Asetek’s RackCDU D2C enable consolidation and mitigate the need for build-outs.  Cost is further reduced by the use of hot water for cooling. CPUs run quite hot (153°F to 185°F) and hotter for memory and GPUs.  The cooling efficiency of water (4000x air) allows it to cool the components with a much smaller temperature difference than air.  This also reduces the power required for server fans.

The data center does not need all the CRACs or CRAHs normally required and rather than needing an extensive chiller plant outside the data center can use cheap dry coolers.  This is a major impact on both CapEx and OpEx.

Monitoring and Alarming is essential for any technology in the contemporary data center.  Asetek’s RackCDU system includes a software suite that provides monitoring, alerts, including temperatures, flow, pressures and leak detection and importantly can report into data center management software suites.

Failure Isolation is a key metric for data centers. Servers using Asetek’s RackCDU use very low pressure and are insolated in closed loops that exchange heat in the CDU with the facilities water loop.  This is an important difference to cooling systems that use a centralized pumping system. Centralized systems require high pressures and hence the risk of high pressure leaks and wide “blast radius.”

Redundancy is one of sacred cows of data centers.  Asetek’s RackCDU D2C CPU and GPU pump /cold plates are drop in replacements for air heat sinks.  One pump is sufficient to drive the required cooling for the server.  Hence a dual CPU, dual GPU or CPU + GPU server contains its own redundant pumping.

Serviceability is a key requirement for any data center hardware system.  Because the Asetek RackCDU is an extension to a standard rack and has independent quick connects for each server, data center facilities teams can remove or replace servers for repair or upgrade as they do today.

Warranty is an issue with installing after market liquid cooling solutions in that it can void the server manufacture’s warranties.  Asetek as also addressed this issue by teaming up with Signature Technology Group (STG), a warranty service and support firm that will maintain coverage for systems that have been upgraded with Asetek’s liquid-cooling technology.

The reality check on data center liquid cooling is that Asetek has moved liquid cooling from an exotic technology to a practical option for data center operators.

Subscribe to HPCwire's Weekly Update!

Be the most informed person in the room! Stay ahead of the tech trends with industy updates delivered to you every week!

Geospatial Data Research Leverages GPUs

August 17, 2017

MapD Technologies, the GPU-accelerated database specialist, said it is working with university researchers on leveraging graphics processors to advance geospatial analytics. The San Francisco-based company is collabor Read more…

By George Leopold

Intel, NERSC and University Partners Launch New Big Data Center

August 17, 2017

A collaboration between the Department of Energy’s National Energy Research Scientific Computing Center (NERSC), Intel and five Intel Parallel Computing Centers (IPCCs) has resulted in a new Big Data Center (BDC) that Read more…

By Linda Barney

Google Releases Deeplearn.js to Further Democratize Machine Learning

August 17, 2017

Spreading the use of machine learning tools is one of the goals of Google’s PAIR (People + AI Research) initiative, which was introduced in early July. Last week the cloud giant released deeplearn.js as part of that in Read more…

By John Russell

HPE Extreme Performance Solutions

Leveraging Deep Learning for Fraud Detection

Advancements in computing technologies and the expanding use of e-commerce platforms have dramatically increased the risk of fraud for financial services companies and their customers. Read more…

Spoiler Alert: Glimpse Next Week’s Solar Eclipse Via Simulation from TACC, SDSC, and NASA

August 17, 2017

Can’t wait to see next week’s solar eclipse? You can at least catch glimpses of what scientists expect it will look like. A team from Predictive Science Inc. (PSI), based in San Diego, working with Stampede2 at the Read more…

By John Russell

Microsoft Bolsters Azure With Cloud HPC Deal

August 15, 2017

Microsoft has acquired cloud computing software vendor Cycle Computing in a move designed to bring orchestration tools along with high-end computing access capabilities to the cloud. Terms of the acquisition were not disclosed. Read more…

By George Leopold

HPE Ships Supercomputer to Space Station, Final Destination Mars

August 14, 2017

With a manned mission to Mars on the horizon, the demand for space-based supercomputing is at hand. Today HPE and NASA sent the first off-the-shelf HPC system i Read more…

By Tiffany Trader

AMD EPYC Video Takes Aim at Intel’s Broadwell

August 14, 2017

Let the benchmarking begin. Last week, AMD posted a YouTube video in which one of its EPYC-based systems outperformed a ‘comparable’ Intel Broadwell-based s Read more…

By John Russell

Deep Learning Thrives in Cancer Moonshot

August 8, 2017

The U.S. War on Cancer, certainly a worthy cause, is a collection of programs stretching back more than 40 years and abiding under many banners. The latest is t Read more…

By John Russell

IBM Raises the Bar for Distributed Deep Learning

August 8, 2017

IBM is announcing today an enhancement to its PowerAI software platform aimed at facilitating the practical scaling of AI models on today’s fastest GPUs. Scal Read more…

By Tiffany Trader

IBM Storage Breakthrough Paves Way for 330TB Tape Cartridges

August 3, 2017

IBM announced yesterday a new record for magnetic tape storage that it says will keep tape storage density on a Moore's law-like path far into the next decade. Read more…

By Tiffany Trader

AMD Stuffs a Petaflops of Machine Intelligence into 20-Node Rack

August 1, 2017

With its Radeon “Vega” Instinct datacenter GPUs and EPYC “Naples” server chips entering the market this summer, AMD has positioned itself for a two-head Read more…

By Tiffany Trader

Cray Moves to Acquire the Seagate ClusterStor Line

July 28, 2017

This week Cray announced that it is picking up Seagate's ClusterStor HPC storage array business for an undisclosed sum. "In short we're effectively transitioning the bulk of the ClusterStor product line to Cray," said CEO Peter Ungaro. Read more…

By Tiffany Trader

How ‘Knights Mill’ Gets Its Deep Learning Flops

June 22, 2017

Intel, the subject of much speculation regarding the delayed, rewritten or potentially canceled “Aurora” contract (the Argonne Lab part of the CORAL “ Read more…

By Tiffany Trader

Nvidia’s Mammoth Volta GPU Aims High for AI, HPC

May 10, 2017

At Nvidia's GPU Technology Conference (GTC17) in San Jose, Calif., this morning, CEO Jensen Huang announced the company's much-anticipated Volta architecture a Read more…

By Tiffany Trader

Reinders: “AVX-512 May Be a Hidden Gem” in Intel Xeon Scalable Processors

June 29, 2017

Imagine if we could use vector processing on something other than just floating point problems.  Today, GPUs and CPUs work tirelessly to accelerate algorithms Read more…

By James Reinders

Quantum Bits: D-Wave and VW; Google Quantum Lab; IBM Expands Access

March 21, 2017

For a technology that’s usually characterized as far off and in a distant galaxy, quantum computing has been steadily picking up steam. Just how close real-wo Read more…

By John Russell

Russian Researchers Claim First Quantum-Safe Blockchain

May 25, 2017

The Russian Quantum Center today announced it has overcome the threat of quantum cryptography by creating the first quantum-safe blockchain, securing cryptocurrencies like Bitcoin, along with classified government communications and other sensitive digital transfers. Read more…

By Doug Black

Nvidia Responds to Google TPU Benchmarking

April 10, 2017

Nvidia highlights strengths of its newest GPU silicon in response to Google's report on the performance and energy advantages of its custom tensor processor. Read more…

By Tiffany Trader

Groq This: New AI Chips to Give GPUs a Run for Deep Learning Money

April 24, 2017

CPUs and GPUs, move over. Thanks to recent revelations surrounding Google’s new Tensor Processing Unit (TPU), the computing world appears to be on the cusp of Read more…

By Alex Woodie

HPC Compiler Company PathScale Seeks Life Raft

March 23, 2017

HPCwire has learned that HPC compiler company PathScale has fallen on difficult times and is asking the community for help or actively seeking a buyer for its a Read more…

By Tiffany Trader

Leading Solution Providers

Trump Budget Targets NIH, DOE, and EPA; No Mention of NSF

March 16, 2017

President Trump’s proposed U.S. fiscal 2018 budget issued today sharply cuts science spending while bolstering military spending as he promised during the cam Read more…

By John Russell

CPU-based Visualization Positions for Exascale Supercomputing

March 16, 2017

In this contributed perspective piece, Intel’s Jim Jeffers makes the case that CPU-based visualization is now widely adopted and as such is no longer a contrarian view, but is rather an exascale requirement. Read more…

By Jim Jeffers, Principal Engineer and Engineering Leader, Intel

Google Debuts TPU v2 and will Add to Google Cloud

May 25, 2017

Not long after stirring attention in the deep learning/AI community by revealing the details of its Tensor Processing Unit (TPU), Google last week announced the Read more…

By John Russell

Six Exascale PathForward Vendors Selected; DoE Providing $258M

June 15, 2017

The much-anticipated PathForward awards for hardware R&D in support of the Exascale Computing Project were announced today with six vendors selected – AMD Read more…

By John Russell

Top500 Results: Latest List Trends and What’s in Store

June 19, 2017

Greetings from Frankfurt and the 2017 International Supercomputing Conference where the latest Top500 list has just been revealed. Although there were no major Read more…

By Tiffany Trader

IBM Clears Path to 5nm with Silicon Nanosheets

June 5, 2017

Two years since announcing the industry’s first 7nm node test chip, IBM and its research alliance partners GlobalFoundries and Samsung have developed a proces Read more…

By Tiffany Trader

Messina Update: The US Path to Exascale in 16 Slides

April 26, 2017

Paul Messina, director of the U.S. Exascale Computing Project, provided a wide-ranging review of ECP’s evolving plans last week at the HPC User Forum. Read more…

By John Russell

Graphcore Readies Launch of 16nm Colossus-IPU Chip

July 20, 2017

A second $30 million funding round for U.K. AI chip developer Graphcore sets up the company to go to market with its “intelligent processing unit” (IPU) in Read more…

By Tiffany Trader

  • arrow
  • Click Here for More Headlines
  • arrow
Share This