Dynamic Path Capacity Allocation for I/O Request Prioritization
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Solution Overview
Problem
Existing path allocation strategies in computer systems do not efficiently divide path capacity, leading to suboptimal system performance and longer response times for high-priority I/O requests, especially in scenarios where dedicated paths are not feasible due to limited capacity and static allocation methods that do not account for actual I/O request dynamics.
Innovation Solution
A dynamic path capacity allocation strategy that identifies and tracks traffic limitations for each path, assigns urgency levels to I/O requests based on performance targets, and selects paths with available capacity to ensure timely transmission of high-priority requests, thereby optimizing the use of path resources and reducing response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If dedicated paths are allocated for high priority I/O requests, then response time for high priority requests is improved, but path capacity utilization is reduced and lower priority requests suffer from longer response times
Solution Approach 1:
The patent implements dynamic path capacity allocation where the system continuously monitors path metrics (such as queue depth, bandwidth availability, and I/O wait times) and adjusts path capacity assignments in real-time. High priority requests can dynamically claim additional path capacity when available, while the system redistributes capacity to lower priority requests when high priority traffic subsides, resolving the contradiction between guaranteed response time and capacity utilization.
Solution Approach 2:
The system changes the allocation parameters of path capacity based on current system state. Instead of fixed dedicated paths, the patent modifies path capacity parameters (bandwidth allocation, queue priorities, transmission credits) dynamically according to the mix of high and low priority requests, allowing optimal resource distribution that adapts to varying workloads and resolves the capacity utilization versus response time trade-off.
2Reliability
If static path allocation is used, then path capacity is guaranteed for each application, but the system cannot adapt to actual I/O request dynamics and real-time conditions
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors path performance metrics (queue depth, transmission success rates, latency) and uses this information to adjust path capacity allocations. This closed-loop feedback allows the system to maintain reliability through capacity guarantees while adapting to actual I/O patterns, resolving the contradiction between static guarantees and dynamic adaptability.
Solution Approach 2:
The system transitions from static path allocation to dynamic capacity assignment where path resources are continuously adjusted based on real-time I/O request characteristics, workload patterns, and path availability. This dynamic approach maintains the reliability of capacity guarantees while providing adaptability to changing conditions, as the system can reassign capacity based on actual demand rather than fixed predetermined allocations.
3Productivity
If all paths are allocated for transmission of any I/O requests, then path capacity utilization is maximized, but response time for sensitive I/O requests increases
Solution Approach 1:
The patent segments path capacity into different allocation classes or queues based on request priority and sensitivity. By dividing the total path capacity into multiple logical channels with different service levels, the system can maximize overall utilization while ensuring that sensitive high-priority requests receive preferential treatment, resolving the contradiction between maximum capacity usage and guaranteed response time.
Solution Approach 2:
The system applies local quality differentiation where different portions of path capacity are assigned different quality attributes (priorities, latency guarantees, bandwidth weights) based on the characteristics of I/O requests. This allows the system to maximize overall productivity while providing enhanced service quality to sensitive requests, resolving the trade-off between capacity utilization and response time performance.
Data Source
AI summary
Methods and systems are disclosed that relate to selecting a path for sending an I/O request from a host to a data storage subsystem from among a plurality of paths from the host to the subsystem. An exemplary method includes identifying a limitation on the traffic level for the plurality of paths, tracking a first metric corresponding to the limitation on the traffic level for each path, and transmitting a first I/O request having an urgency level other than the highest urgency level by one of the plurality of paths whose first metric does not exceed its limitation on the traffic level.