A Storage Area Network (SAN) is a dedicated high-speed network that provides block-level access to consolidated storage resources, traditionally built on Fibre Channel or iSCSI — and now increasingly on NVMe/TCP.
A Storage Area Network separates storage I/O traffic from general-purpose LAN traffic by running it on a dedicated network fabric. In a traditional FC SAN, this means dedicated FC switches, FC Host Bus Adapters (HBAs) in every server, and optical fiber cabling between servers and storage arrays. The SAN presents storage to each server as locally attached block devices — servers do not share filesystems over the SAN; instead, each server formats its allocated volumes with a local filesystem (NTFS, ext4, XFS) or uses them directly as raw block devices for databases and virtual machine disk images.
IP-based SANs using iSCSI eliminated the need for dedicated FC infrastructure by running block storage traffic over standard Ethernet TCP/IP. This dramatically reduced SAN costs and made block storage accessible to organizations that could not justify the expense of FC hardware. However, iSCSI retained the SCSI command set and its limitations — including the single-queue concurrency model — which limited its performance at high IOPS relative to FC at the same link speed.
The NVMe/TCP SAN represents the current evolution: block storage over Ethernet using NVMe's native command set and multi-queue architecture. An NVMe/TCP SAN looks like an iSCSI SAN from an infrastructure perspective (standard Ethernet switches, standard NICs), but delivers dramatically higher IOPS, lower latency, and better CPU efficiency. Modern NVMe/TCP SANs built on 25 GbE or 100 GbE Ethernet infrastructure can deliver over 1 million IOPS per host with sub-100 µs latency — performance that was previously achievable only with purpose-built all-flash arrays and FC SANs.
NVMe/TCP is the protocol enabling the next generation of SANs. Where traditional SANs required careful separation of storage and application traffic on dedicated FC fabrics, NVMe/TCP SANs can converge storage and application traffic on the same high-speed Ethernet fabric with appropriate QoS policies. This convergence simplifies datacenter network design and reduces the number of distinct network fabrics that operations teams must manage.
| Generation | Protocol | Year | Max IOPS (typical) |
|---|---|---|---|
| 1st | Fibre Channel (FCP) | 1994 | ~500K |
| 2nd | iSCSI | 2004 | ~400K |
| 3rd | NVMe/TCP | 2018+ | 1.5M+ |