Host Bus Adapter Priority Tagging for VM Visibility in FC SANs
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Solution Overview
Problem
Current Fibre Channel (FC) storage area networks (SANs) lack end-to-end priority tagging capability due to variability in target-side FC driver support among vendors, hindering VM visibility and fabric-wide analytics, and are incomplete without universal adoption of priority tagging features.
Innovation Solution
Implementing priority tagging capabilities independently of target devices by modifying host bus adapters and Fibre Channel switches to tag and interpret VM tags within the Priority field of FC frames, using existing standards and configurations to ensure compatibility and visibility across the FC fabric, even when target devices are not priority tagging capable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If priority tagging is implemented only when both host and target are capable, then target compatibility is maintained, but VM visibility and fabric analytics are lost
Solution Approach 1:
The host bus adapter performs priority tagging in advance (at the host side) before frames reach the target, so that VM identification is established prior to any potential target processing. This ensures VM visibility is maintained even when targets are not priority tagging capable, as the tagging action occurs before the frame needs to be processed by the target.
Solution Approach 2:
The host bus adapter acts as an intermediary that bridges the capability gap between priority tagging-capable hosts and non-capable targets. It translates and applies VM tags to frames locally, serving as a mediator that enables VM visibility functionality without requiring the target to have priority tagging capability.
2Loss of information
If host bus adapters tag frames independently of target capability, then VM visibility is achieved, but target devices may misinterpret tags as priority values
Solution Approach 1:
The patent applies different handling logic for different target types. For category-1 targets (non-priority capable), the host adapter tags frames with VM tags in the Priority field without causing misinterpretation. For category-3 targets (priority capable), the system uses different mechanisms. This localized adaptation ensures VM visibility is achieved without causing harmful misinterpretation at the target.
Solution Approach 2:
The system changes the parameter interpretation based on target capability. When communicating with category-1 targets, the Priority field is used to carry VM tags. The host bus adapter modifies the framing and interpretation parameters locally, allowing VM tag insertion without creating ambiguity for the target device.
3Loss of information
If universal priority tagging support is implemented, then end-to-end VM visibility is achieved, but device complexity and implementation time increase
Solution Approach 1:
Instead of requiring full end-to-end priority tagging capability (which would be excessive and complex), the patent implements partial action by having only the host bus adapter perform tagging. This partial implementation achieves sufficient VM visibility functionality without requiring all devices in the path to support the full priority tagging protocol.
Solution Approach 2:
The priority tagging functionality is extracted from the target device requirements and placed at the host bus adapter level. By taking out the tagging responsibility from the target side, the system achieves VM visibility without imposing complex requirements on target devices, thereby reducing overall implementation complexity.
Data Source
AI summary
A host bus adapter of a target device is associated with a Fibre Channel driver and is connected to a Fibre Channel switch fabric. The host bus adapter receives from the switch fabric an inbound frame having a header including a source identifier and a virtual machine (VM) tag, stores a mapping between the source identifier and the VM tag, and passes the inbound frame to the Fibre Channel driver. The host bus adapter receives from the Fibre Channel driver an outbound frame having a header including a destination identifier, and determines, based on the mapping, whether there is a match at least between the source identifier of the inbound frame and the destination identifier of the outbound frame. If there is a match, the host bus adapter tags the header of the outbound frame with the VM tag, and transmits the tagged outbound frame to the switch fabric.