Passive State Indication via SCSI Response Payload Truncation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In data storage systems, existing technologies lack effective methods to indicate a passive state for a device, leading to inefficient path management and potential I/O operation failures, as they fail to accurately communicate the availability of paths for I/O operations.
Innovation Solution
A method is introduced where a response with a 'good' status and a varying-sized payload, truncated before the device identifier, is sent to indicate a passive state, allowing the host to determine the path's availability for I/O operations, and multipathing functionality is used to select alternative paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard response format with complete device identifier is used, then the response provides full device information, but it cannot indicate a passive state for the path
Solution Approach 1:
The patent extracts the device identifier from the response payload by truncating the payload before the device identifier location. This allows the response to indicate a passive state for the path while maintaining compliance with the SCSI standard's good status requirement. The host can detect the passive state by observing the truncated payload length.
Solution Approach 2:
The patent changes the payload length parameter of the response to indicate a passive state. By setting the payload length to a value that truncates the response before the device identifier, the system communicates path unavailability without violating the SCSI standard. This parameter change allows differentiation between active and passive states while maintaining standard compliance.
2Reliability
If the response payload includes the device identifier, then the path is indicated as active, but it cannot indicate a passive state
Solution Approach 1:
The patent uses the response payload length as feedback to communicate path state to the host. By controlling whether the device identifier is included in the response, the system provides clear feedback about path availability. The host interprets the presence or absence of the device identifier to determine if the path is active or passive.
3Productivity
If existing path management methods are used, then the system can handle multiple paths, but it cannot effectively indicate when a path is passive and unavailable
Solution Approach 1:
The patent performs preliminary action by indicating the passive state through the truncated response before any I/O operations are attempted on the inactive path. This allows the host to proactively identify unavailable paths and redirect I/O operations to active paths, improving overall system efficiency and preventing failed operations.
Data Source
AI summary
Described are techniques for indicating a state associated with a device. A request is received over a path for information about a device. A response to the request is sent. The response indicates a state regarding the device on the path. The response has a response status of good and a payload of a varying size. The payload is truncated at a location prior to that at which a device identifier for the device is expected. In accordance with the response, a state regarding the device on the path is determined.