This week Lenovo took the wraps off the ThinkSystem SD650 high-density server with third-generation direct water cooling technology developed in tandem with partner Leibniz Supercomputing Center (LRZ) in Germany. The servers are designed to operate using warm water, up to 45°C for general deployments and for special bid projects up to 50°C, lowering datacenter power consumption 30-40 percent compared to traditional cooling methods, according to Lenovo.
Nearly 6,500 of the ThinkSystems SD650s featuring Intel Xeon Platinum (Skylake) processors interconnected with Intel Omni-Path Architecture will be put into production at LRZ this year, providing the supercomputing center with 26.7 petaflops of peak performance, housed in a little over 100 racks.
The SuperMUC-NG supercomputer will be deployed with Lenovo’s new Lenovo Intelligent Computing Orchestrator (LiCO) and the Lenovo Energy Aware Runtime (EAR) software, a technology that dynamically optimizes system infrastructure power while applications are running.
“Pretty much all the investments that we made to get to exascale LRZ is taking advantage of in this bid we won with them,” said Scott Tease, executive director, HPC and AI at Lenovo in an on-site briefing at Lenovo’s headquarters in Morrisville, North Carolina, last week. “We will start building systems and start shipping them in March; the floor will be ready by the end of April, and move-in starts in early May. We’ll be ready to do acceptance in September with final customer acceptance in November.”
The direct-water cooled design of the SD650 enables 85-90 percent heat recovery; the rest can easily be managed by a standard computer room air conditioner. The hot water coming off the servers can be recycled to warm buildings in the winter, as LRZ does with its petascale SuperMUC cluster, but the technology developed by Lenovo for SuperMUC-NG actually transforms that heat energy back into cooling for networking and storage components.
The endothermic magic trick only works with “high quality heat,” Lenovo thermal engineer Vinod Kamath told us, so LRZ’s SD650 servers were designed to be able to consume 50°C inlet temperatures. Water is piped out of the servers at 58-60°C depending on workload and sent through an adsorption chiller, where it is converted to chilled 20°C water suitable for cooling storage and networking components.
If you’re using chilled water to cool servers you can’t really take advantage of the economics of the adsorption chiller. With 60°C inlet water, the efficiency of Lenovo’s adsorption chiller is about 60 percent. If your energy source has a higher temperature, say 80-90°C then the extraction is even more efficient, but 60°C is good enough to realize significant savings.
Adsorption chilling will be applied to half the nodes of the next-gen LRZ install, generating about 600 kilowatts of chilled water capacity. This translates into more than 100,000 Euros a year in saved energy cost at the European site, where the rate for energy is about 16-18 Eurocents per kilowatt-hour (roughly 2-3 times the cost for similar sites in the United States). Lenovo claims a 45-50 percent energy savings with the endothermic reaction versus a traditional compressor, dropping the datacenter PUE from 1.6 to less than 1.1.
The cooling solution can be traced back to 2012, when IBM (Lenovo acquired IBM’s x86 server business in 2014) was approached by LRZ to develop a system that was both powerful and extremely energy efficient. The first production implementation to come out of the partnership was the 9,200 node SuperMUC at LRZ, that achieved a number four ranking on the June 2012 Top500 list. The custom motherboard, developed with Intel, was cooled by water piped over compute and memory and back out of the system. LRZ used the hot water coming out of the system to heat parts of their building, which offset some of their overall energy costs.
The partnership also led to the deployment of the CooLMUC-2 cluster at LRZ in 2016. That system was the prototype for the next-gen LRZ cooling solution; it uses hot outlet water to drive adsorption chillers that generate refrigerated water, which is then used to cool some of the cluster’s disk storage systems.
“When we started doing this it was all about power cost,” said Tease. “It was all about datacenter optimization. Those things are still important, but we’re starting to see people recognize that water will allow them to do things that air can’t. I can do special processors that I can’t do with air; I can achieve densities that in the future I can’t do with air. We are really excited that we’ve got such a unique design, what we believe is an industry-leading design point as the market is coming to where we’ve been.”
The Lenovo ThinkSystem SD650 dual-node tray is designed for high-performance computing (HPC), large-scale cloud, and heavy simulations. One 6U NeXtScale n1200 enclosure houses up to six of these trays, accommodating a total of 12 SD650 compute nodes, 24 Intel Xeon Scalable Processors, 9.2TB of memory, 24 SFF SSDs or 12 SFF NVMe drives, and 24 M.2 boot drives.
The SD650 HPC servers have no system fans (except on the power supplies at the back of the rack), and operate at lower temperatures when compared to standard air-cooled systems. Chillers are not needed for most customers, which translates into further savings and a lower total cost of ownership. The new server supports high-speed EDR InfiniBand and Omni-Path fabrics as well as standard SSDs, NVMe SSDs, and M.2 boot SSDs.
In demoing the SD650, Kamath showed how the water supply comes in through the 6U NeXtScale n1200 chassis and flows into the servers. “We have a calibrated flow split between the processor and the memory to tune the heat transfer,” he said. “We recognize that networking devices are power hungry now and will be more so in the future, so the water that splits to the memory is coupled to a drive, an NVMe or SSD, and coupled to a network device, like ConnectX-5 or OPA, and then the water flows and connects back to conduction point.”
Lenovo designed the system with special attention to the next-generation memory technologies. Each server has 12 DIMM slots for truDDR4 memory but there are actually 16 slots total. Four have been reserved for 3D-XPoint (also known as Apache Pass or AEP memory). The cooling system is able to extract 10 watts on standard DIMMs, and for 3D XPoint and other higher-powered memory future designs, they’ll have two water lines going through a DIMM that can consume 18 watts. Lenovo also provides a handy DIMM removal tool making it easy to swap out memory.
Lenovo has been picking up major HPC system awards in Europe since acquiring IBM’s x86 business three and a half years ago. It has the fastest supercomputer in Spain, Italy, Denmark, Norway, Australia, Canada, and soon in Germany with LRZ. It has also been making in-roads with its warm water cooling solutions. In addition to its systems at LRZ, it has warm water HPC installations at Peking University (first ever in China), India Space Administration (first ever in India), and a multi-university system in Norway.
Liquid cooling is becoming mainstream in HPC, especially in environments where constraints on space boost density requirements or in expensive energy zones. Lenovo tells customers that when it comes to electricity prices, anything over 15 cents per kilowatt hour will provide a return on investment within one year. Another benefit of removing more heat is that CPUs can run in “turbo” mode nonstop, which can squeeze an additional 10 percent performance from them.
The SD650 is managed by Lenovo Intelligent Computing Orchestrator (LiCO), a management suite with an intuitive GUI that supports management of large HPC cluster resources and accelerates development of AI applications. LiCO works with the most common AI frameworks, including TensorFlow, Caffe and Microsoft CNTK.