Centralized vs. Distributed Pumping for Rack-based Direct Liquid Cooling

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Superior performance and reliability has been realized in data centers that utilize centralized pumping systems. Centralized pumping assemblies offer multiple advantages over distributed pumping systems, and we’ve mapped out the comparisons to prove it.

Feature CoolIT Systems Centralized Pumping Distributed Pumping
Low-Profile Cold Plates With a total height of 15.6mm, the CoolIT R3 Passive Cold Plate easily fits in all server and blade configurations. Each cold plate has an integrated pump that renders it too high to fit into dense HPC server blade configurations.
Moving Parts No moving parts, nothing to fail, never removed from server until the server itself is retired. Each cold plate is a pump, a point of failure that must be mainatined and removed from the server upon failure.
Points of Failure A rack with 100 processors requires only 2 pumps and they are redundant.  A rack with 100 processors has 100 points of failure, each one on the server.
Ease of Maintenance Pump maintenance is simple, less frequent and completed inside the heat exchanger not the servers.  Pump maintenance must be performed inside each server – time consuming and high chance of damaging other components.
Balancing Flow Through Servers Centralized pumping through passive cold plates maintains appropriate flow distribution across all processors with minimal pressure changes from supply and return manifolds. Multiple pumps increase pressure in the return manifold relative to the supply manifold. Because of this pressure differential:

    1. A pump failure in a single pump loop will result in a reverse of coolant flow from return (warm) to supply (cool).
    2. In a single pump failure within a dual pump loop scenario, the remaining operating pump will not have enough power to overcome the high pressure in the return manifold resulting in reduced coolant flow.
    3. Heterogeneous processor environments struggle to overcome pressure challenges due to the mixture of single and dual pump loops. The single pump loops can be starved of flow.
Manifold Complexity Only requires a single manifold to maintain appropriate flow to all servers. A full rack requires three separate manifolds in order to counter the effect of over-pressurized return manifolds. This results in more connections, each being a failure point on the manifold.
High Pressure Facility Water In the multiple rack scenario (CHx650), the higher pressure facility water stops at the CHx650 and is not brought to the racks. With the single rack (CHx40) scenario, the higher pressure facility water is brought to the rack and stops at the CHx40 Module heat exchange system. In all scenarios of distributed pumping, the higher pressure facility water is brought directly to the rack and stops at the heat exchange system.
Cost of Cold Plates Very low cost as no pump required. Higher cost to pay for the pump in each cold plate.

Proven technology: DCLC is helping businesses achieve maximum performance, efficiency and density

DCLC™ technology has been put to work in a variety of collaborative efforts. CoolIT Systems recently teamed up with Intel and Supermicro to create an innovative HPC cluster, Cherry Creek, that ranked 400 on the Top500 list of supercomputers and an impressive #41 on the Green 500 list. The cluster uses CoolIT’s Rack DCLC™ AHx35 solution and Supermicro’s ultra-dense FatTwin server platform, featuring 9936 cores with a peak performance of 131.2 teraflops. The system consumed a total of 74.25kW of power even though each Supermicro FatTwin node featured dual Intel Xeon processors and three Intel Xeon Phi coprocessors that were generating over 1,000 watts of heat per node.

A collaboration between CoolIT Systems and the University of Leeds has been set up to analyse the influence of direct liquid cooling on demand within cloud based workload algorithms. The 45U Rack DCLC has been installed at the university to enhance their research into energy efficient aspects of data centers, by combining the expertise from two disciplines to understand the intersection of cloud scheduling algorithms with a fine controlled cooling on demand methodology.

CoolIT supports a wide variety of private, government, and academic organizations with their various compute initiatives. CoolIT has established itself as an experienced innovator in developing safe and reliable DCLC solutions for today’s most demanding data center users.

Learn more about CoolIT’s performance, efficiency and density benefits for data centers, big or small, with Direct Contact Liquid Cooling.

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Centralized vs. Distributed Pumping in Rack-based Direct Liquid Cooling: