Storage Controller Tag Group Management for SAS Chip Reset Recovery
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Solution Overview
Problem
In storage apparatus using SAS protocol, chip resets lead to increased failure processing recovery time and potential tag number overlaps, especially when multiple drives are connected, causing delays and inefficiencies in IO processing.
Innovation Solution
The storage apparatus manages multiple tag numbers by separating them into groups, allowing the controller to assign different tag numbers before and after a chip reset, preventing overlaps and enabling quicker recovery and processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the controller waits for a given period of time after chip reset before assigning tag numbers, then tag number overlap is prevented, but failure processing recovery time increases
Solution Approach 1:
The patent segments the tag number space into multiple groups (e.g., group 0 and group 1). When a chip reset occurs, the controller switches to a different group than the one used before the reset. This segmentation allows immediate tag number assignment after reset without waiting for a given period, preventing overlap while reducing recovery time.
2Reliability
If the controller resets all drives after chip reset, then tag number overlap in drives is prevented, but IO processing time increases significantly
Solution Approach 1:
The patent extracts the tag number management function from the drive reset process. Instead of resetting all drives after a chip reset, the controller only manages tag number assignment at the controller level by switching between tag number groups. This eliminates the need for time-consuming drive resets while maintaining tag number uniqueness.
Solution Approach 2:
The patent applies local quality by differentiating the reset scope: only the controller undergoes chip reset, while drives remain operational. The tag number group switching is applied locally at the controller level, allowing drives to continue processing IO operations without interruption.
3Device complexity
If the controller uses the same tag numbers before and after chip reset, then tag number assignment is simple, but tag number overlap occurs preventing IO processing
Solution Approach 1:
The patent introduces dynamics by making the tag number group assignment changeable based on the chip reset state. The controller dynamically switches between different tag number groups (e.g., from group 0 to group 1) when a chip reset occurs, rather than using a fixed tag number assignment scheme. This dynamic adaptation prevents tag number overlap while maintaining relatively simple management.
Data Source
AI summary
Provided is a storage apparatus including a plurality of storage devices which store data, a controller which executes data input/output processing to the storage devices, and a processor which transmits/receives information with the controller, wherein the controller manages a plurality of different tag numbers by separating the tag numbers into a plurality of groups, and upon receiving a first command from the processor, assigns a tag number belonging to one group among the plurality of groups to the first command, and transfers the first command to a designated storage device, and, upon subsequently receiving an instruction for a chip reset from the processor, executes a chip reset, and, upon subsequently receiving a second command from the processor, assigns a tag number belonging to a group which is different from the group used before the chip reset to the second command, and transfers the second command to a designated storage device.