SAN, NAS, and DAS are the three ways to connect storage to servers. The difference comes down to two questions: does the storage hand out blocks or files, and does it travel over a direct cable, your regular Ethernet network, or a dedicated storage fabric? DAS (Direct-Attached Storage) bolts disks straight to one server for block-level access. NAS (Network-Attached Storage) is an appliance on your Ethernet LAN that serves files to many clients over NFS or SMB. SAN (Storage Area Network) is a shared array that presents block-level volumes, called LUNs, to multiple servers across a separate high-speed fabric such as Fibre Channel or iSCSI. This guide explains how each model works, where it fits, and how to choose.

SAN vs NAS vs DAS at a glance

Use this table for a quick side-by-side; the sections below explain each model and its trade-offs in depth.

DAS: Direct-Attached Storage

DAS is storage that connects directly to a single server or workstation with no network in between - the internal drive bays in a server, or an external enclosure wired over SAS, SATA, NVMe, or PCIe. The host sees the drives at the block level, exactly as if they were internal, and its own operating system owns the file system.

Because there is no network hop, DAS delivers low latency and high throughput, and it is the simplest and most economical way to add capacity. The trade-off is sharing: the storage belongs to that one host, so other machines cannot reach the data directly. Scaling means adding drives or daisy-chaining enclosures rather than growing a shared pool. External SAS JBOD arrays such as Dell PowerVault direct-attached storage extend DAS well beyond the bays inside the chassis, and some support dual-host attach for basic failover.

DAS fits local boot volumes, a database or application that lives on a single server, backup targets, and capacity expansion for one host where shared access is not required.

NAS: Network-Attached Storage

A NAS is a self-contained file-server appliance that plugs into your existing Ethernet LAN. It owns its own disks and file system and shares folders to clients at the file level using standard protocols - NFS for Linux and Unix, SMB/CIFS for Windows, and often AFP, FTP, or object (S3) access on top. Any authorized client on the network can mount a share and read or write files at the same time.

That makes NAS the easiest shared-storage model to deploy and manage: no specialized cabling, no separate fabric, and centralized permissions, quotas, and snapshots. Because traffic rides the general-purpose network and the appliance handles the file system, NAS is optimized for file workloads rather than the lowest-latency block I/O. Throughput is bounded by the LAN and the appliance, though 10/25/40GbE links and SSD caching close much of that gap.

NAS fits shared file storage, home directories, team and departmental shares, media libraries, and backup or archive targets - anywhere many users or servers need access to the same files.

SAN: Storage Area Network

A SAN is a dedicated network that carries block-level storage. A shared array exports logical volumes called LUNs, and each server on the fabric sees its assigned LUN as if it were a locally attached disk - the server, not the array, puts a file system on it. That fabric is kept separate from the LAN and is built on Fibre Channel, or on iSCSI, which carries the same SCSI block commands over standard Ethernet and TCP/IP.

Keeping storage traffic on its own fabric gives a SAN high performance, low latency, and independent scalability - capacity grows on the array without touching the servers. Presenting shared block volumes is also what makes clustering and virtualization work: multiple hosts can access the same LUNs, enabling live migration (such as vMotion), high availability, and shared datastores in VMware, Hyper-V, and Proxmox. The cost is complexity - a SAN needs switches, host bus adapters or dedicated NICs, multipathing, and the expertise to run it, which is why it is the premium option. Refurbished arrays such as Dell EqualLogic iSCSI SAN storage make SAN economics far more approachable.

SAN fits virtualization clusters, mission-critical and high-transaction databases, and any environment that needs shared block storage with high availability and room to grow.

How to choose between SAN, NAS, and DAS

Match the model to the workload, not the other way around:

• Choose DAS when a single server needs fast, private, low-cost storage - local databases, boot volumes, or capacity for one host.
• Choose NAS when many users or servers need to share files and you want the simplest centralized solution on your existing network.
• Choose SAN when many servers need shared block storage with the performance and high availability that clustering and busy databases demand.

Most data centers run all three - DAS inside the servers, a NAS for file shares, and a SAN behind the virtualization cluster. The right foundation starts with the right server: browse refurbished Dell PowerEdge servers and configurable platforms like the Dell PowerEdge R750, or explore refurbished enterprise storage arrays to pair the storage model to your workload. Not sure which fits? Request a quote and our team will help you size it.

Frequently asked questions

What is the main difference between SAN, NAS, and DAS?

DAS attaches storage directly to one server for private, block-level access. NAS is a networked appliance that shares files to many clients over the LAN using NFS or SMB. SAN is a dedicated fabric that presents shared block-level volumes (LUNs) to multiple servers. In short: DAS is direct and block, NAS is networked and file, and SAN is a dedicated network and block.

Is NAS block-level or file-level storage?

NAS is file-level: the appliance owns the file system and serves whole files over protocols like NFS and SMB/CIFS. DAS and SAN are block-level, handing raw blocks to the host, which then applies its own file system.

What is the difference between Fibre Channel and iSCSI in a SAN?

Both carry block SCSI commands. Fibre Channel uses a dedicated FC fabric with its own switches and host bus adapters for very high, predictable performance. iSCSI carries the same block commands over standard Ethernet and TCP/IP, so it reuses familiar networking and is typically easier and more economical to deploy, ideally on an isolated or dedicated network segment.

Can DAS be shared between multiple servers?

Generally no - DAS is dedicated to the host it is connected to. Some external SAS enclosures support dual-host attach for basic failover, but true many-server sharing is exactly what NAS (files) and SAN (blocks) are designed for.

Which is better for virtualization, SAN or NAS?

Both are used successfully. Shared block storage over a SAN is the traditional choice for clustered datastores and the lowest-latency database I/O, while NAS over NFS is widely used with VMware and other hypervisors and is simpler to run. The key requirement for features like live migration and high availability is shared storage - SAN or NAS - rather than DAS.

What is a LUN?

A LUN (logical unit number) is a block-level volume that a SAN array exports to a server. The server sees the LUN as if it were a local disk and formats it with its own file system, even though the capacity lives on the shared array.