SAS Expander BROADCAST(CHANGE) Primitive Suppression
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Solution Overview
Problem
Current Serial Attached SCSI (SAS) storage systems face significant processing overhead and communication bandwidth utilization due to the propagation of BROADCAST(CHANGE) primitives and associated SAS Discovery processes in response to configuration changes, which can delay I/O requests.
Innovation Solution
Implementing a method in SAS storage systems to detect temporary configuration changes and prevent the propagation of BROADCAST(CHANGE) primitives if the changes are restored within a predetermined time period, using enhanced SAS expanders with configuration change control logic to selectively manage the propagation of configuration change information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If BROADCAST(CHANGE) primitives are propagated throughout the SAS domain in response to configuration changes, then configuration information is kept current across all components, but processing overhead and communication bandwidth utilization increase significantly
Solution Approach 1:
The patent changes the parameter of BROADCAST(CHANGE) propagation by introducing a suppression mechanism that prevents propagation when the change is temporary (link restored within timeout period). This selective parameter change reduces unnecessary processing while maintaining configuration accuracy for permanent changes.
Solution Approach 2:
The expander acts as an intermediary between the link change and the rest of the SAS domain. It monitors link status changes and intelligently decides whether to propagate BROADCAST(CHANGE) primitives, serving as a mediator that filters out temporary changes before they reach other components.
2Reliability
If SAS Discovery process is initiated in response to BROADCAST(CHANGE) primitives, then the new configuration is determined and distributed to all components, but I/O request processing is delayed until Discovery completes
Solution Approach 1:
The patent changes the parameter of Discovery process initiation by introducing a condition that suppresses Discovery when the link change is temporary. This parameter change ensures that I/O processing is not unnecessarily delayed while still maintaining configuration accuracy for permanent changes.
Solution Approach 2:
The expander performs preliminary action by detecting temporary link changes and preventing the propagation of BROADCAST(CHANGE) primitives before they can trigger unnecessary SAS Discovery processes. This preliminary anti-action avoids the harmful effect of I/O delays caused by redundant Discovery operations.
3Reliability
If configuration changes are propagated throughout the SAS domain, then all components are notified of changes, but communication bandwidth is consumed by unnecessary propagation of temporary changes
Solution Approach 1:
The patent changes the parameter of configuration change propagation by introducing a suppression mechanism that prevents propagation when the change is temporary. This selective parameter change reduces communication bandwidth consumption while maintaining notification reliability for permanent changes.
Solution Approach 2:
The expander serves as an intermediary that monitors link status and intelligently decides whether to propagate configuration change notifications. It filters out temporary changes, preventing unnecessary communication bandwidth consumption while ensuring that permanent changes are properly notified throughout the domain.
Data Source
AI summary
Methods and structure for improved configuration management of a storage system. A storage system comprises one or more storage controllers coupled with a plurality of storage components (e.g., storage devices and switching components). The coupling often comprises a switched fabric communication structure. Configuration changes normally propagated throughout the components of the networked storage system are prevented by detecting temporary changes in the configuration that are restored to the original configuration within a predetermined period of time. In a Serial Attached SCSI (SAS) storage system, SAS expanders and initiators of the network may be enhanced in accordance with features and aspects hereof to prevent propagation of BROADCAST(CHANGE) primitives when a temporary configuration change is restored within the timeout period. Configuration changes may include temporary loss of link communications for a link of the expander and/or removal and insertion of a storage device coupled with the expander.