Lane-Based Multiplexing for SAS Physical Links
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Solution Overview
Problem
Current Serial Attached SCSI (SAS) systems face limitations in flexible and dynamic PHY multiplexing, where a single physical link can only support two connections with alternating data transmission, restricting the number of connections and link rates that can be managed efficiently.
Innovation Solution
A SAS device with a controller capable of time division multiplexing and de-multiplexing a physical link into multiple lanes, allowing for dynamic selection and management of lanes based on link rates for multiple connections, enabling flexible and efficient data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single physical link multiplexes two connections with alternating data transmission, then the device complexity is reduced, but the adaptability and productivity are limited
Solution Approach 1:
The patent segments the single physical link into multiple logical channels, each capable of independent data transmission. Instead of alternating between two connections, the PHY is divided into multiple lanes that can simultaneously service multiple connections, thereby increasing adaptability while maintaining structural simplicity.
Solution Approach 2:
The patent implements dynamic lane allocation where the controller can flexibly assign different numbers of lanes to different connections based on their link rate requirements. This dynamic resource allocation enables the system to adapt to varying connection demands without increasing physical hardware complexity.
2Device complexity
If a single physical link multiplexes two connections with alternating data transmission, then the device complexity is reduced, but the productivity is reduced
Solution Approach 1:
The patent enables continuous data transmission across multiple connections by eliminating the alternating transmission pattern. Multiple lanes allow parallel data flow, ensuring that the physical link remains continuously utilized for productive data transfer rather than idle during alternating cycles.
Solution Approach 2:
The patent merges multiple data streams from different connections into the single physical link through multiple lanes. This combining approach allows simultaneous transmission of multiple connections over the same physical medium, significantly improving overall data handling efficiency.
3Ease of operation
If the PHY is logically divided into two separate entities, then the ease of operation is improved for simple multiplexing, but the adaptability to various link rates is reduced
Solution Approach 1:
The patent creates a universal lane allocation mechanism that can accommodate various link rates (1.5G, 3G, 6G, 12G) by dynamically assigning appropriate numbers of lanes to each connection. This multi-functional approach allows the same physical infrastructure to serve diverse speed requirements without complicating the operational model.
Data Source
AI summary
Methods and structure for lane-based multiplexing of physical links are provided. In one embodiment, a Serial Attached Small Computer System Interface (SAS) device is provided. The SAS device comprises a physical link and a controller. The controller is able to time division multiplex the physical link into multiple lanes, and to manage a first connection along one or more of the lanes of the physical link. The controller is further able to detect a request for a second connection, to determine a link rate for the second connection, to select a number of additional lanes at the physical link based on the link rate for the second connection, and to manage the second connection along the additional lanes while the first connection is being managed.