SAS Expander Priority Control for Burst Length Mismatch
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Solution Overview
Problem
In storage systems using SAS protocol, drives with different burst lengths experience performance degradation due to uneven data transmission, where high-performance drives with small burst lengths are particularly affected, leading to reduced efficiency when connected with drives having larger burst lengths.
Innovation Solution
A connection apparatus that adjusts the priority of connection requests based on burst length information, increasing the wait time for drives with small burst lengths to ensure fair and efficient data transmission by modifying the AWT in connection requests, allowing them to establish connections preferentially within a predetermined successive connection count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If drives with different burst lengths are connected in the same SAS network, then the system can support diverse storage devices, but drives with small burst lengths experience performance degradation due to uneven data transmission
Solution Approach 1:
The patent applies local quality by adjusting the AWT parameter specifically for drives with small burst lengths, rather than applying a uniform setting to all drives. The expander identifies drives based on their burst length characteristics and applies differentiated priority adjustments, allowing each drive type to operate optimally within the same network.
Solution Approach 2:
The patent changes the AWT parameter dynamically based on the drive's burst length characteristics. By modifying this timing parameter, the system adjusts the connection establishment priority to compensate for the inherent performance differences between drives with varying burst lengths, thereby balancing overall system efficiency.
2Reliability
If drives with small burst lengths are given higher priority to improve their performance, then data transmission fairness improves, but the connection management complexity increases
Solution Approach 1:
The patent modifies the AWT parameter based on burst length characteristics to adjust connection priority. This parameter change approach provides a simple mechanism to achieve performance fairness without requiring complex scheduling algorithms or multiple control structures.
Solution Approach 2:
The expander automatically identifies drive characteristics and adjusts AWT values without external intervention. The system self-regulates connection priorities based on observed burst length patterns, eliminating the need for manual configuration or complex external control mechanisms.
3Speed
If the AWT is adjusted to increase connection priority for certain drives, then connection establishment speed improves for those drives, but the overall system response time becomes more variable
Solution Approach 1:
The patent applies differentiated AWT adjustments based on local drive characteristics (burst length) rather than applying uniform timing to all drives. This localized approach optimizes connection establishment for specific drive types while maintaining predictable overall system behavior through systematic parameter management.
Solution Approach 2:
The expander periodically monitors connection patterns and burst length characteristics, adjusting AWT values in a systematic manner. This periodic adjustment mechanism helps stabilize system response time by preventing extreme variations while still providing priority optimization for drives with small burst lengths.
Data Source
AI summary
A connection apparatus that connects a plurality of storage units and a controller that establishes connection with the respective storage units in response to a connection request issued from each of the plurality of storage units and accesses the storage units includes a processor; and a memory, wherein the processor transmits a connection request selected based on priority information that represents priority associated with the connection among a plurality of received connection requests to the controller, the priority information being stored in the memory, and changes priority information included in a connection request received from a certain storage unit among the plurality of storage units so that the priority information has higher priority than the priority information included in connection requests received from the other storage units for a period where a connection request is successively received from the certain storage unit and a predetermined condition is satisfied.