Disk Adapter I/O Redistribution for Storage Load Balancing
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Solution Overview
Problem
Existing data storage systems often underutilize resources as only a single disk adapter (DA) actively manages physical storage devices, leading to inefficiencies when another DA needs to take over in case of failure, and there is no efficient method to rebalance logical device distribution among multiple DAs in response to configuration changes.
Innovation Solution
A method and system for dynamically redistributing logical devices among multiple disk adapters based on configuration changes, where each logical device is assigned a primary active DA, allowing concurrent management and I/O operations across multiple DAs, and implementing a distribution technique that balances workload and properties like compression rates and device types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single disk adapter actively manages physical storage devices, then resource utilization is simplified and management is easier, but resource utilization efficiency deteriorates when another DA needs to take over in case of failure
Solution Approach 1:
The patent segments the management of physical storage devices across multiple disk adapters, where each DA can independently manage and service I/Os to the same physical devices. This divides the previously centralized management function into distributed segments, enabling concurrent access and improving resource utilization while maintaining manageable complexity through defined ownership rules for each logical device
Solution Approach 2:
Each disk adapter is designed with multi-functionality to service I/Os for multiple logical devices that map to the same physical storage devices. Rather than dedicating specific physical devices to single DAs, each DA becomes universal in its capability to manage any logical device's I/O operations, enabling flexible failover and load balancing
2Productivity
If multiple disk adapters concurrently service I/Os to the same physical storage devices, then resource utilization improves and failover efficiency improves, but system complexity increases
Solution Approach 1:
The system implements feedback mechanisms where the storage system monitors configuration changes and automatically triggers redistribution of logical devices among disk adapters. This closed-loop feedback approach manages the complexity of multi-DA coordination by automatically adjusting the system state in response to detected changes, eliminating the need for complex manual configuration management
Solution Approach 2:
The redistribution process is self-service in nature, where the storage system autonomously determines and executes the optimal distribution of logical devices among disk adapters based on configuration changes. The system serves itself by automatically rebalancing workloads without requiring external intervention, thereby managing complexity through automation rather than manual procedures
3Productivity
If logical devices are redistributed among disk adapters in response to configuration changes, then workload balance is maintained and resource utilization is optimized, but system disruption increases during rebalancing
Solution Approach 1:
The system performs preliminary detection of configuration changes and proactively initiates redistribution before significant performance degradation occurs. By detecting changes early and executing rebalancing in advance, the system maintains optimal workload distribution while minimizing disruption, as the transition is planned and executed before it impacts ongoing operations
Data Source
AI summary
Techniques for performing configuration may include: determining an initial distribution of logical devices among disk adapters, wherein the initial distribution assigns each logical device a designated disk adapter as a primary active disk adapter servicing I/Os directed to the logical device, wherein the logical devices have storage provisioned from a RAID group including physical storage devices, wherein the disk adapters concurrently issue I/Os to each of the physical storage devices; detecting a configuration change; and responsive to detecting a configuration change, performing first processing. The first processing may include determining, in accordance with the configuration change, a redistribution of the logical devices among the disk adapters; and draining pending I/Os. The configuration change may include adding or removing a logical device provisioned from the RAID group. Performing a first operation on a storage device of the RAID group may include synchronous draining of I/Os of the storage device.