The Three Pillars of Protocol Selection
Pillar 1: The Performance Profile
While all modern protocols on high-speed Ethernet are fast, they are not the same. The key difference is latency.
NVMe/RoCE (RDMA over Converged Ethernet) is the undisputed performance gold standard, offering the lowest possible latency by bypassing the host CPU's networking stack for direct memory access. In benchmark tests, RoCE can deliver up to 66% lower write latency compared to NVMe/TCP, making it essential for applications where microseconds matter.
NVMe/TCP offers a significant leap in performance over iSCSI, reducing latency by up to 34%.3 It delivers many of the benefits of the NVMe command set over standard, ubiquitous TCP/IP networks.
iSCSI on modern 10/25/100GbE networks is a proven workhorse. While its latency is higher than NVMe-based protocols due to TCP/IP overhead, it provides more than enough throughput for a vast range of enterprise workloads.
Pillar 2: Operational Complexity & Required Skillset
A faster protocol is only valuable if your team can deploy and manage it effectively.
iSCSI & NVMe/TCP are operationally simple. They run over standard Ethernet and the well-understood TCP/IP stack that your network and systems teams have managed for decades. This simplicity accelerates deployment and reduces the risk of misconfiguration.
NVMe/RoCE demands a meticulously configured "lossless" network. Achieving this requires deep expertise in Data Center Bridging (DCB) technologies like Priority-based Flow Control (PFC) and Explicit Congestion Notification (ECN).2 This complexity is often a significant barrier to adoption for teams without specialized skills.
Pillar 3: Total Cost of Ownership (TCO)
The financial impact extends beyond the initial purchase price.
iSCSI & NVMe/TCP are the most cost-effective options, as they run on standard, commodity Ethernet NICs that are already in your servers.
NVMe/RoCE carries a higher cost. It requires more expensive RDMA-capable NICs (RNICs) and, to guarantee lossless performance, often relies on higher-end, deep-buffered switches. This investment, while typically 30% less than legacy Fibre Channel, is still more significant that iSCSI & NVMe/TCP and must be justified by a clear business requirement for extreme low-latency performance.
Guide: NVMe-OF
Maximize your storage performance with NVMe-oF on Ethernet. This page dissects NVMe/TCP (easy deployment, standard networks) versus NVMe/RoCE (ultra-low latency RDMA, needs lossless DCB), helping you choose the optimal transport by detailing trade-offs, hardware, and network requirements.
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Guide: Switch Selection for Storage Networking
When storage traffic meets standard Ethernet, performance suffers. Learn what makes a switch storage-ready — from deep buffers to DCB — and how to build a high-performance, lossless Ethernet SAN for protocols like NVMe-oF and iSCSI.
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Guide: RoCE vs. iWARP
Curious whether RoCE or iWARP is right for your storage fabric? This guide demystifies RDMA technology and explores how each protocol impacts latency, deployment complexity, and NVMe-oF readiness—so you can choose with confidence.
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Guide: iSCSI
A practical guide to iSCSI in modern storage networks. Learn how iSCSI works, where it fits in Fibre Channel migrations, and when to choose it over NVMe/TCP.
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Architecture: NVMe/TCP
Explore our detailed Reference Architecture for NVMe/TCP in VMware Environments. Proven deployment guidance to ensure performance, visibility, and scale.
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Architecture: NVMeOF/RoCEv2
Explore our detailed Reference Architecture for NVMeOF/RDME with RoCEv2 for ultra-high performance environments. Proven deployment guidance to ensure performance, visibility, and scale.
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Architecture: Nutanix HCI + Arista
A scalable, low-latency reference architecture using Nutanix + Arista EVPN/VXLAN with support for metro and multi-site replication.
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