Uniform Drive Performance via TCB Allocation
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Solution Overview
Problem
Storage systems with heterogeneous storage devices of different performance capabilities face challenges in maintaining uniform performance levels during drive qualification and operation.
Innovation Solution
The system creates arrays for different drive types, certifies drives at the same performance level, and computes stage and destage maximum values. At runtime, it sets Task Control Blocks (TCBs) to uniform values based on minimum performance levels across drive types, ensuring uniform performance by limiting actual TCBs and adding delays as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If heterogeneous storage devices with different performance capabilities are used to increase storage capacity and adaptability, then storage system versatility is improved, but performance uniformity deteriorates
Solution Approach 1:
The storage system segments drives by type and performance capability into separate arrays. Each array contains drives of the same type certified at the same performance level, allowing the system to maintain performance uniformity within each segment while supporting heterogeneous drive types across the overall system.
Solution Approach 2:
Different arrays are configured with different maximum TCB values based on their specific drive type characteristics. Fast drives receive higher TCB allocations while slower drives receive lower allocations, ensuring each array operates at its optimal performance level without affecting other arrays.
2Productivity
If the number of TCBs is increased to improve data staging and destaging throughput, then productivity is improved, but performance inconsistency across different drive types worsens
Solution Approach 1:
The system dynamically adjusts the maximum TCB parameter based on drive type and performance capability. Each drive type has a predetermined maximum TCB value that optimizes throughput while maintaining consistent performance characteristics across different drive types.
3Productivity
If performance benchmarks are run for each drive type to compute optimal TCB values, then performance optimization is improved, but system complexity and measurement difficulty increase
Solution Approach 1:
Performance benchmarks are executed during drive qualification before drives are deployed into production arrays. This preliminary characterization establishes predetermined maximum TCB values for each drive type, eliminating the need for complex runtime performance tuning and simplifying ongoing system management.
Data Source
AI summary
Provided are techniques for task adjustment for uniform performance of drives. Arrays are created for different drive types. Performance benchmarks are run for each of the arrays to compute a stage maximum value and a destage maximum value for each of the drive types. At run time, in response to determining that a mode indictor indicates a uniform performance mode, a maximum number of stage Task Control Blocks (TCBs) are set to a stage maximum uniform value and a maximum number of destage TCBs are set to a destage maximum uniform value. The stage of first data is performed using an actual number of stage TCBs that do not exceed the maximum number of stage TCBs. The destage of second data is performed using an actual number of destage TCBs that do not exceed the maximum number of destage TCBs.