SAS Switch Bulk Discovery Zone Filtering
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Solution Overview
Problem
Current large SAS storage networks experience increased discovery time and traffic due to the stacking of SAS switches, leading to delays and potential starvation of lower priority tasks, as each initiator device must perform full discovery and manage multiple serial protocol commands.
Innovation Solution
Implementing a bulk discovery process with zone-based filtering, where SAS switches provide updated and aggregated data models to registered initiator devices, reducing the need for full fabric discovery and unconditioned broadcast of change primitives, and allowing devices to register for bulk discovery on a push or pull basis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If SAS switches are stacked to enable communication between switches and devices in respective domains, then device accessibility is improved, but discovery time increases dramatically
Solution Approach 1:
The patent segments the fabric discovery process into two distinct phases: bulk discovery (performed once when a device is first added to the fabric) and change discovery (performed when topology changes occur). This segmentation allows initiator devices to register with SAS switches for bulk discovery, receiving a complete data model of the fabric once, and then rely on the switch to notify them of subsequent changes, thereby eliminating repeated full fabric discoveries while maintaining access to stacked switches.
Solution Approach 2:
The patent implements preliminary action by having SAS switches proactively maintain and update a data model of the fabric topology, and by having initiator devices register in advance for bulk discovery notifications. When topology changes occur, the switch already has the updated information ready to send to registered initiators, eliminating the need for initiators to perform time-consuming discovery procedures and enabling rapid notification of fabric changes.
2Measurement precision
If initiator devices perform full fabric discovery to obtain updated data models, then data model accuracy is improved, but network traffic increases
Solution Approach 1:
The patent extracts the burden of fabric discovery from initiator devices and transfers it to SAS switches. The switch performs the discovery function centrally, maintains an accurate data model, and sends only the necessary updates to registered initiators. This extraction eliminates the need for initiators to send numerous SMP and SSP commands across the fabric, dramatically reducing network traffic while the switch ensures data model accuracy through its centralized discovery process.
3Reliability
If SAS switches send unconditioned BROADCAST (CHANGE) primitives to all initiator devices, then notification completeness is improved, but interrupt overhead increases
Solution Approach 1:
The patent applies local quality by having SAS switches send targeted change notifications only to specific initiator devices that are registered for bulk discovery and have indicated their interest in particular types of fabric changes. Instead of broadcasting to all initiators unconditionally, the switch filters and directs notifications locally to the appropriate devices, maintaining complete notification coverage for registered initiators while eliminating unnecessary interrupts to devices that do not need the information.
Data Source
AI summary
An example disclosed is directed to a switch. The switch includes a communication interface and a discovery module. The discovery module is to receive a registration request for bulk discovery from an initiator device via the communication interface. The discovery module is further to receive a change indication specifying that a change has occurred in a fabric associated with the switch, and update a data model based on the received change indication to generate an updated data model. The discovery module then filters the updated data model to generate a filtered data model, and sends the filtered data model to the initiator device via the communication interface.