What is the longest supported cable length for use with DirectFlash shelves?

DirectFlash Shelves (DFS) connect to the FlashArray controllers using high-speed protocols (typically RoCE - RDMA over Converged Ethernet) that require high-fidelity signal integrity. Due to the high bandwidth (50Gb or 100Gb speeds) and low latency requirements of the NVMe-oF (NVMe over Fabrics) protocol used for backend connectivity, the physical cabling length is strictly limited.

Pure Storage officially supports a maximum cable length of 3 meters for connecting DirectFlash Shelves to the controller or for daisy-chaining shelves (where supported). Cables longer than 3 meters (such as 5m or 7m) introduce signal attenuation and latency that can destabilize the backend fabric, leading to CRC errors, path flapping, or drive disconnections.

Implementation Engineers must ensure that the rack layout allows the shelves to be placed within this 3-meter radius of the controllers. Typically, shelves are racked immediately above or below the controller chassis to minimize cable run distance. Attempting to span across multiple racks using longer, unsupported cables will result in an unsupported configuration and likely immediate I/O errors.

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