What are the key differences and similarities between FC and NVMe over Fabrics?

1 What is SAN?

SAN stands for storage area network, which is a dedicated network of servers, storage devices, and switches that provides high-speed data transfer and access. SAN enables multiple hosts to share storage resources, such as disks, arrays, or tapes, without interfering with each other. SAN also offers advantages such as scalability, redundancy, security, and management.

3 What is NVMe-oF?

NVMe-oF is a protocol that extends the NVMe interface to remote storage devices over a fabric. NVMe is a standard that defines how to communicate with solid-state drives (SSDs) using the PCI Express (PCIe) bus. NVMe-oF enables hosts to access SSDs over various transport options, such as FC, Ethernet, or InfiniBand. NVMe-oF aims to reduce latency, increase parallelism, and improve efficiency for flash-based storage.

4 How do FC and NVMe-oF differ?

FC and NVMe-oF differ in several aspects, such as architecture, performance, compatibility, and cost. FC uses a switched fabric topology, where each device has a unique address and a direct path to any other device. NVMe-oF uses a host-to-target model, where each host has a queue pair (QP) that connects to a target's controller. FC has lower latency than NVMe-oF, but NVMe-oF has higher throughput and IOPS than FC. FC requires FC-specific hardware and software, while NVMe-oF can leverage existing Ethernet or InfiniBand infrastructure. FC is more expensive and complex to deploy and maintain than NVMe-oF, but also more mature and stable.

5 How do FC and NVMe-oF compare?

FC and NVMe-oF are not mutually exclusive, but rather complementary protocols that can coexist and interoperate in SAN environments. FC can support NVMe-oF as a transport option, using the FC-NVMe standard that defines how to map NVMe commands and responses to FC frames. This allows FC users to benefit from the advantages of NVMe-oF, such as higher performance and lower CPU utilization, without replacing their existing FC infrastructure. Similarly, NVMe-oF can support FC as a legacy protocol, using the NVMe-FCP standard that defines how to map SCSI commands and responses to NVMe-oF QPs. This allows NVMe-oF users to access FC-based storage devices, such as arrays or tapes, without losing compatibility.

6 What are the best practices for SAN design?

When designing a SAN, there are various factors to consider, such as the type and size of storage devices, the number and location of hosts, bandwidth and latency needs, budget and resources available, and security and reliability policies. To ensure successful design, it is important to plan ahead and document goals, needs, and constraints. Additionally, the protocol, topology, switch configuration, redundancy, load balancing, zoning, masking, monitoring tools, encryption, authentication, authorization, and auditing mechanisms should be chosen and optimized for performance and availability. Furthermore, regular maintenance is essential for maintaining your SAN by updating firmware and software drivers while performing backups, tests, and audits.