NAS vs SAN vs DAS: Storage Solutions Compared

Choosing the right storage architecture is one of the most important infrastructure decisions for any business. NAS, SAN, and DAS are the three fundamental approaches — each with its own strengths, limitations, and ideal use cases. Understanding the differences leads to better decisions and avoids costly misinvestments.

The Three Storage Architectures at a Glance

DAS — Direct Attached Storage

DAS is the simplest form of storage: hard drives or SSDs are connected directly to a server — via SATA, SAS, or NVMe. There is no network between server and storage. The internal hard drive in your PC is essentially DAS.

Advantages:

• Maximum performance (no network overhead)
• Low latency
• Simple setup
• Low cost

Disadvantages:

• Usable by only one server (no sharing)
• Scaling only by adding drives to the same server
• No centralized management
• Backup requires additional solutions

NAS — Network Attached Storage

NAS provides storage over the network — as file shares via protocols like SMB (Windows), NFS (Linux), or AFP (macOS). A NAS is a standalone system with its own operating system that delivers files over the standard network (Ethernet/IP) to multiple clients simultaneously.

Advantages:

• Access from any number of clients simultaneously
• Centralized data storage and permissions management
• Integrated features (snapshots, replication, compression)
• Easy integration into existing networks

Disadvantages:

• Network overhead (higher latency than DAS)
• Performance dependent on network speed
• File-based access (not optimal for databases)

SAN — Storage Area Network

SAN provides storage at the block level — over a dedicated storage network separated from the regular data network. Typical protocols include iSCSI (over Ethernet) and Fibre Channel. To the server, a SAN volume looks like a local hard drive.

Advantages:

• Block-level access (optimal for databases and VMs)
• High performance and low latency
• Multiple servers can access the same storage
• Dedicated network prevents bottlenecks

Disadvantages:

• Higher complexity in setup and management
• Additional network infrastructure required (for Fibre Channel)
• Higher costs
• Specialized expertise necessary

Detailed Comparison: NAS vs SAN vs DAS

Criterion	DAS	NAS	SAN
Access Method	Block (local)	File (SMB/NFS)	Block (iSCSI/FC)
Network	None (direct)	Standard Ethernet	Dedicated (iSCSI/FC)
Shared Access	No (1 server)	Yes (many clients)	Yes (multiple servers)
Typical Latency	< 0.1 ms	1–5 ms	0.5–2 ms
Scalability	Limited	Good	Very good
Complexity	Low	Medium	High
Cost	Low	Medium	High
Ideal For	Single server, local workloads	File shares, backups	VMs, databases

Which Solution for Which Use Case?

File Server and Network Drives → NAS

The classic use case for NAS: employees access shared files via network drives. A TrueNAS system with ZFS additionally provides automatic checksums, snapshots for quick recovery, and native SMB/NFS support.

Virtualization (VMs and Containers) → SAN or DAS

Virtual machines on Proxmox VE require fast block-level access. For single servers, DAS is the most performant solution — local NVMe SSDs offer the lowest latency. For cluster environments with multiple Proxmox nodes, a SAN (e.g., TrueNAS with iSCSI) or a hyperconverged solution with Ceph is the right choice.

Backup and Archiving → NAS

Backup data is file-based and benefits from deduplication and compression. A NAS with large capacity and ZFS is the most cost-effective solution for backup storage. Combined with Proxmox Backup Server, it creates a highly efficient backup infrastructure.

Databases → SAN or DAS

Databases (SQL Server, PostgreSQL, MySQL) require low latency and high IOPS throughput. Block-level access via DAS (local SSDs) or SAN (iSCSI) is mandatory. NAS-based access via NFS or SMB is not recommended for databases.

Video Surveillance → NAS

IP cameras deliver continuous data streams written to a NAS over the network. TrueNAS with large HDD capacity and ZFS compression is a cost-effective solution for video recording.

Combining NAS and SAN: In Practice

In reality, many businesses use a combination. A single TrueNAS system can simultaneously function as both NAS and SAN:

• NAS function: SMB/NFS shares for file server, backups, media
• SAN function: iSCSI targets for Proxmox VMs and databases

This significantly simplifies the infrastructure — one system, two access methods. ZFS manages all storage uniformly with checksums, snapshots, and compression, regardless of whether data is delivered as files or blocks.

iSCSI vs Fibre Channel

Two options are available for the SAN protocol:

Criterion	iSCSI	Fibre Channel
Network	Standard Ethernet (10/25/100 GbE)	Dedicated FC switches (16/32/64 Gbit)
Cost	Low (existing switches usable)	High (special FC HBAs + switches)
Performance	Very good (10 GbE+)	Excellent
Latency	Good	Very low
Complexity	Medium	High
Recommendation	SMBs	Large enterprises, high-load

For SMBs, we recommend iSCSI over 10-Gigabit Ethernet. The performance is sufficient for the vast majority of workloads, and existing network infrastructure can be leveraged. Fibre Channel only becomes worthwhile for very high latency and throughput requirements.

Sizing: How Much Storage Do I Need?

A basic formula for initial planning:

• File server: Current needs × 1.5 (growth buffer) + snapshot reserve (20%)
• Virtualization: Sum of all VM disks × 1.3 (thin provisioning, snapshots)
• Backup: Production data × 3 (with daily backup, 30-day retention, with deduplication)
• RAID overhead: With RAIDZ2 (recommended): Usable capacity ≈ Total capacity × (n-2)/n

Frequently Asked Questions

Which is better: NAS or SAN?

Neither is universally better. NAS is suited for file shares and backups, SAN for VMs and databases. Many businesses use both — often on the same TrueNAS system.

Does our SMB need a SAN?

If you run Proxmox clusters with multiple nodes and need shared storage for live migration, yes. For single servers, DAS (local SSDs) is sufficient. iSCSI over 10 GbE is the cost-effective SAN solution for SMBs.

Can TrueNAS be both NAS and SAN simultaneously?

Yes. TrueNAS simultaneously supports SMB/NFS (NAS) and iSCSI (SAN) on the same system. This reduces hardware costs and simplifies management.

How many IOPS do I need?

This depends on the workload. File server: 500–2,000 IOPS. Virtualization: 5,000–50,000 IOPS. Databases: 10,000–100,000+ IOPS. SSDs typically deliver 50,000–500,000 IOPS, HDDs 100–200 IOPS.

What does a NAS cost for an SMB?

A TrueNAS system with 4× 16 TB HDDs (RAIDZ2, 32 TB usable) starts at approximately €2,500 for hardware. Add 10 GbE network cards (€100 each). The software is free.

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Need guidance choosing the right storage architecture? Contact us — we plan and implement tailored storage solutions for your business.