Considerations for Selecting a Row-Based CDU for your Data Center

June 28, 2024
Ian Reynolds, Senior Project Engineer with CoolIT Systems, outlines the factors you need to consider when selecting the best CDU for your data center's needs.

Selecting the right row-based Coolant Distribution Unit (CDU) for your data center is essential for achieving peak performance and efficiency. To make an informed decision, it's important to evaluate key factors related to your facility, CDU performance capabilities, CDU features including redundancy, monitoring and serviceability, and manufacturing location and practices. This article provides an outline to help you navigate these considerations and select the best CDU for your needs. 

Facility Considerations

Choosing a CDU starts with a thorough understanding of your facility's design and constraints. Consider the following:

  • Facility Water Availability: The availability of facility water will drive the decision between the two main categories of row-based CDUs: liquid-to-liquid or liquid-to-air. Liquid-to-air CDUs are preferable if there is limited facility water available for ease of deployment. If facility water is already plumbed into the area where the CDUs will be installed (or is feasible to be brought in), liquid-to-liquid CDUs are preferable due to their increased capacity.
  • Physical Deployment: The size and weight of the CDU must align with your building’s constraints, such as elevator capacity, floor loading limits, and available space. Proper assessment ensures smooth installation and operation, avoiding costly modifications or downtime.
  • Secondary Fluid Network (SFN) Buildout: Efficiently planning the connection between the row-based CDUs and the racks is crucial for efficient operation due to its impact on the overall system pressure drop, serviceability, and scalability of the system.

CDU Performance 

Two main performance points to consider are secondary flow rate and overall heat load capability. 

  • Secondary Flow Rate: The CDU’s flow rate, driven by pump performance, directly affects heat removal efficiency from the chip. As Thermal Design Powers (TDPs) rise, the demand for higher flow rates increases. Along with the higher flow rates, system pressure drops are trending upwards, so ensuring adequate pump performance is crucial.
  • Heat Load Capability: The performance of heat exchangers or coils determines the CDU's ability to dissipate heat from the Direct Liquid Cooling (DLC) system back to the facility. Lack of capacity and efficiency at the heat exchanger or coil level drives up the temperature of fluid going to the IT and reduces the heat load that can be handled.

Redundancy, Monitoring, and Serviceability

When a DLC system goes down, there is the potential to lose all supported systems within a matter of minutes, so it is important to consider the following features of a CDU solution: 

  • Redundancy: Prevent downtime by ensuring your CDUs have internal redundancy within units and multiple units working together. This is critical for maintaining uninterrupted operations.
  • Monitoring and Interfaces: Advanced monitoring systems alert operators to potential issues in real-time. Interfaces like MODBUS, SNMP, SFTP, SSH, and SMTP provide comprehensive oversight and control.
  • Serviceability: Simple design and easy access to critical components ensures swift maintenance and minimal disruption, maintaining high system uptime and efficiency.

Manufacturing and Sourcing

Consider a CDU manufacturer’s sourcing practices as well as its location: 

  • Manufacturing Location: When CDUs are manufactured in Canada, lead times are significantly more stable. Additionally, check the manufacturer’s ability to collaborate between its headquarters and manufacturing facility. Proximity results in improved collaboration and communication resulting in superior product quality and reliability.
  • Integrated Engineering Approach: Purchasing from a company deeply involved in engineering DLC systems ensures comprehensive design and manufacturing processes for CDUs, enhancing overall system integration and performance.

Choose the Best CDU for Your Data Center

Selecting the appropriate CDU for your row-based data center involves careful consideration of several factors, including facility design, performance metrics, redundancy, and manufacturing practices. By understanding these key aspects, you can make an informed decision that optimizes cooling efficiency and reliability in your data center.

About the Author

Ian Reynolds

Ian Reynolds is a Senior Project Engineer with CoolIT Systems, focusing on solution design and deployment of liquid cooling solutions for high-performance computing (HPC), AI data centers and enterprise environments globally. 

CoolIT Systems specializes in scalable liquid cooling solutions for the world’s most demanding computing environments, partnering with global processor and server design leaders to develop the most efficient and reliable liquid cooling solutions for their leading-edge products. Click here to learn more about CoolIT’s CDUs and to download product brochures.

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