4. SAN Architecture

Outcome

Draw a host-to-LUN path, identify every component and distinguish connectivity from redundancy and application availability.

Level: Foundation · Time: 45 minutes · Prerequisite: Data Protection and Recovery

Learn

host HBA A → fabric A switch → target port/controller A ┐
                                                       ├→ mapped LUN
host HBA B → fabric B switch → target port/controller B ┘
                         ↑
                   multipath policy

An initiator starts I/O. A target receives it. A fabric transports frames but does not create a LUN mapping. Zoning controls fabric visibility; array masking/mapping controls which initiator may access which LUN. Both must be correct.

Dual fabrics should avoid shared switches and inter-fabric dependencies. A surviving path is not sufficient if failover exceeds the application’s timeout.

Practice

Open the SAN Failure-Domain Lab. Fail one component at a time, then fail correlated components. Record reachability, redundancy and recovery-time results separately.

Check your understanding

1. Why can a host see a target port but not its LUN?
2. What is the difference between reachable and redundant?
3. Which shared component could defeat an apparently dual-path design?

Production boundary

Real designs depend on host drivers, array ownership, ALUA behavior, timeouts, queueing, fabric policy and tested failover sequences.

Next step

Continue to Fibre Channel Fabric Operations.