Storage Area Network (SAN)
- Network architecture that provides block-level access to storage devices - creates dedicated high-speed network separate from LAN for storage traffic
- Enables multiple servers to access shared storage pools as if they were locally attached drives
- Centralizes storage management while providing high performance and redundancy for enterprise environments
Key Characteristics
- Block-level access: Storage appears as raw disk blocks to servers (not file-level like NAS)
- Dedicated network: Uses separate infrastructure from production LAN to avoid bandwidth contention
- High availability: Multiple paths between servers and storage for redundancy
- Scalability: Can add storage and servers independently without major reconfiguration
SAN Protocols and Technologies
| Protocol | Transport | Speed | Use Case |
|---|---|---|---|
| Fibre Channel (FC) | Native FC | 8/16/32 Gbps | Traditional enterprise SAN, highest performance |
| iSCSI | TCP/IP over Ethernet | 1/10/25/40 Gbps | Cost-effective SAN over existing network |
| FCoE | Fibre Channel over Ethernet | 10/25/40 Gbps | Converged infrastructure, reduces cables |
| NVMe over Fabrics | Various (FC, Ethernet, InfiniBand) | 25+ Gbps | Next-generation flash storage |
Network Components
- HBA (Host Bus Adapter): Network card that connects servers to SAN fabric
- SAN switches: Specialized switches that route storage traffic (different from Ethernet switches)
- Storage arrays: Centralized storage systems with multiple disk drives and controllers
- Zoning: Logical segmentation that controls which servers can access which storage (similar to VLANs)
SAN vs. NAS Comparison
| Aspect | SAN | NAS |
|---|---|---|
| Access method | Block-level | File-level |
| Protocol | FC, iSCSI, FCoE | NFS, SMB/CIFS |
| Performance | Higher (direct block access) | Lower (file system overhead) |
| Complexity | High (specialized skills needed) | Medium (standard networking) |
| Cost | Higher (specialized hardware) | Lower (standard Ethernet) |
| Use case | Databases, virtualization | File shares, backups |
iSCSI Implementation Details
- Initiator: Client that requests storage access (typically server with software initiator)
- Target: Storage device that provides block storage over network
- IQN (iSCSI Qualified Name): Unique identifier format for initiators and targets
- Discovery: Process where initiators find available targets on network
- Authentication: CHAP (Challenge Handshake Authentication Protocol) commonly used
Practical Network Considerations
- Jumbo frames (9000 MTU) recommended for iSCSI to reduce CPU overhead
- Multipathing: Configure multiple network paths for redundancy and load balancing
- VLAN segmentation: Isolate storage traffic from other network traffic for security and performance
- QoS: Prioritize storage traffic to ensure consistent performance
Notes
- iSCSI is most relevant for CCNA - uses standard TCP/IP networking unlike specialized Fibre Channel
- Separate storage and production networks - storage traffic can saturate links and impact user experience
- Consider latency requirements - database applications need low-latency storage access, file shares are more tolerant
- Plan IP addressing carefully - storage networks often use dedicated subnets (e.g., 192.168.100.0/24 for iSCSI)
- Boot from SAN capabilities allow diskless servers but require careful network design for reliability
- Security consideration: Storage networks carry sensitive data - implement proper access controls and encryption where required