Back to: Storage Area Network (SAN) Storage
A Storage Area Network (SAN) is a high-speed network that provides access to consolidated, block-level storage. The logical flow of data in a SAN follows a structured path to ensure efficient and reliable communication between storage devices and servers. Here’s a step-by-step breakdown of the logical data flow in a SAN environment:
1. Initiator (Host) Requests Data
- The process starts with a server (host) that needs to read or write data.
- The Host Bus Adapter (HBA) in the server generates a SCSI request (SCSI command) and sends it through the SAN fabric.
2. SAN Fabric Receives the Request
- The request passes through the SAN switch, which is responsible for routing the data.
- The switch uses protocols like Fibre Channel (FC), iSCSI, or NVMe-oF to transport the data.
- The switch ensures zoning and logical partitioning are in place to allow only authorized traffic.
3. Storage Controller Processes the Request
- The SAN fabric routes the request to the appropriate storage controller in the storage array.
- The storage controller interprets the SCSI command and determines where the data is located in the storage system.
4. Data Retrieval from Storage
- The storage controller accesses the appropriate LUN (Logical Unit Number) and retrieves the requested data.
- If the data is being written, the storage controller ensures it is stored in the correct block location.
5. Data Transfer Back to the Host
- The retrieved data is sent back through the SAN fabric.
- The SAN switch routes the response to the requesting server.
- The host’s HBA receives the response and passes it to the operating system.
6. Application Receives Data
- The application running on the server processes the received data.
- If necessary, additional processing, caching, or indexing occurs.
Logical Flow Diagram
Key SAN Concepts for Logical Data Flow
- Initiators & Targets: The host (initiator) requests data from the storage device (target).
- Fabric Switching: The SAN switch manages the routing of data packets.
- Zoning & LUN Masking: Controls which servers can access specific storage devices.
- Multipathing: Ensures redundancy and load balancing in data flow.
- Protocols: Common ones include Fibre Channel (FC), iSCSI, FCoE, and NVMe-oF for data transport.