SAN

In short: Storage Area Network — a separate, usually high-performance network that connects servers to central storage (hard disk/SSD arrays), separate from the normal data network.

In more detail: Unlike classic network storage (NAS), which shares files via standard network protocols, a SAN provides storage at the block level — to connected servers it looks like a locally attached hard disk. Common in data centres, often implemented via Fibre Channel or iSCSI.

In Depth

The decisive technical difference between SAN and NAS lies in the level of abstraction: a NAS provides finished file systems via network protocols such as SMB or NFS — a connected client sees “files and folders”. A SAN, on the other hand, delivers raw storage blocks without a file system of its own — the connecting server formats these blocks itself with a file system of its choice, just as with a locally installed hard disk. This makes a SAN particularly suitable for applications that need full control over the storage layout, e.g. database servers or virtualisation platforms.

Transmission usually runs via Fibre Channel (a separate, dedicated fibre network specifically for storage traffic, very high-performance but expensive) or iSCSI (SCSI storage commands packed into normal IP packets, running over ordinary Ethernet infrastructure, cheaper but tending to be slower). Large companies use SANs to provide storage centrally and redundantly for many servers at the same time, instead of each server having its own isolated hard disks.

See also: Hard drives, SSDs