Fast Access Channel Host Request Processing Using Track Status
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Solution Overview
Problem
In storage environments using fast access channels like PCIe, host requests experience latency and failure if the target track is being accessed by another process, as the system must wait for a lock to be released, often exceeding processing thresholds.
Innovation Solution
The use of track status information, specifically an active or inactive status indicated by an active bit in the cache control block, determines whether to process a host request on a fast access channel, failing requests if the track is active to avoid latency and allowing immediate access if inactive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the system waits for lock release on a fast access channel, then the host request can be processed on the fast channel, but the latency exceeds the processing threshold
Solution Approach 1:
The system checks the active bit in the cache control block before processing the host request on the fast access channel. This preliminary action determines in advance whether the target track is currently being accessed, allowing the system to avoid waiting for lock release and instead fail the request early, causing the host to resend on a slower channel.
Solution Approach 2:
If the active bit indicates the track is currently accessed, the system skips the waiting process entirely and immediately fails the request on the fast channel. This rushing through the decision process prevents the latency that would occur from waiting for lock release, accepting the trade-off of using a slower channel instead.
2Productivity
If the system processes requests on the fast access channel without checking track status, then processing is faster, but conflicts occur when tracks are accessed by multiple processes
Solution Approach 1:
The system performs a preliminary check of the active bit in the cache control block before allowing fast channel processing. This advance verification ensures that data access safety is maintained by detecting conflicts before they occur, while still allowing high-speed processing to proceed when no conflicts exist.
Solution Approach 2:
The active bit in the cache control block provides feedback about the current access status of the target track. This feedback mechanism allows the system to make informed decisions about whether to proceed with fast channel processing or fail the request, balancing productivity and reliability based on real-time track status information.
Data Source
AI summary
Provided are a computer program product, system, and method for using track status information on active or inactive status of track to determine whether to process a host request on a fast access channel. A host request to access a target track is received on a first channel to the host. A determination is made as to whether the target track has active or inactive status. The target track has active status when at least one process currently maintains a lock on the target track that prevents access and the target track has inactive status when no process maintains a lock on the target track that prevents access. Fail is returned to the host to cause the host to resend the host request on a second channel in response to the target track having the active status. The first channel has lower latency than the second channel.