The valid transfer path for re-using iSCSI cards during a controller upgrade is from a FlashArray//X R2 to a FlashArray//X R3. The hardware architecture and form factor for specific PCIe-based iSCSI cards are compatible between these two generations. This allows for the migration of existing connectivity hardware, preserving port configuration and reducing costs during a non-disruptive upgrade (NDU). The M-series controllers use a different chassis and internal architecture, making their components incompatible with the later X-series (XR2/XR3) controllers.

B. M > XR2/3: M-series controllers and X-series controllers have fundamentally different hardware architectures and chassis designs. Their internal components, including iSCSI cards, are not interchangeable.

C. M > XR2: This is a specific instance of the incompatibility mentioned for option B. Cards from an M-series controller cannot be physically installed or used in an XR2 controller.

1. Pure Storage FlashArray™ //X R3 Upgrade Guide: In the section detailing the upgrade process from an //X R2 system, the guide explicitly lists which components can be transferred. It states, "The following components can be transferred from the existing //X R2 controllers to the new //X R3 controllers: ... 4-port 10/25GbE iSCSI/RoCE PCIe Card." This directly confirms the compatibility for the XR2 > XR3 path.

2. Pure Storage FlashArray™ Hardware Guide (for M-Series and X-Series): A comparison of the hardware guides for M-series (e.g., FA-M70) and X-series (e.g., FA-XR2) controllers reveals different physical dimensions, slot layouts, and component part numbers. The documentation for M-series upgrades to X-series involves a full chassis replacement, with no provision for transferring internal PCIe cards, confirming the M > X incompatibility.

3. Pure Storage Evergreen™ Storage Program Documentation: The principles of the Evergreen program detail how non-disruptive upgrades are performed. Documentation on "Upgrade Flex" bundles for moving between generations (e.g., //X R2 to //X R3) specifies the re-use of compatible components like certain HBAs, whereas upgrades from older platforms like the M-series require a full hardware refresh.