Protocol Compatibility: While NVMe-over-Fabrics (NVMe-oF) is the future of high-performance storage, support for it within specific hypervisor ecosystems varies. In the context of Microsoft Hyper-V, especially in older or standard Ethernet-switched environments, iSCSI remains the most mature, widely supported, and native protocol for block storage.
Ethernet Constraints: The question specifies an Ethernet-switched environment. This immediately rules out NVMe/FC (NVMe over Fibre Channel), as that requires dedicated Fibre Channel switching infrastructure and HBAs, not standard Ethernet.
NVMe/RoCE vs. iSCSI: While NVMe/RoCE (RDMA over Converged Ethernet) runs on Ethernet, it requires specialized NICs (RDMA-capable) and a specific switch configuration (PFC/LFC) to ensure a lossless fabric. Hyper-V has specific requirements for RoCE (often tied to SMB Direct for File services), but for general block storage volumes in a standard Ethernet environment, iSCSI is the "best suited" due to its ease of deployment, native Windows initiator support, and lack of requirement for specialized lossless hardware.
Pure Storage Best Practices: Pure Storage FlashArrays provide industry-leading iSCSI performance. When using iSCSI with Hyper-V, Pure recommends using the native Windows MPIO (Multi-Path I/O) with the "Least Queue Depth" policy to ensure optimal load balancing across the Ethernet fabric.