Log Structured Array Data Migration via LBA Mapping
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Solution Overview
Problem
The proliferation of computers and computing systems has led to a need for efficient data storage, but traditional host-centered data copy processes consume processing resources and network bandwidth, and ODX Offload Copy data migration operations result in hole formation within Log Structured Arrays (LSAs), increasing host I/O penalties and complexity.
Innovation Solution
A storage system controller and method that divides block-based storage devices into logical units (LUNs) to manage data migration operations within LSAs, using ODX Copy Offload instructions to directly transfer data between storage devices, reducing hole formation by mapping and unmapping LBA locations efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional host-centered data copy processes are used, then data can be transferred between storage devices, but processing resources and network bandwidth are consumed
Solution Approach 1:
The patent extracts the data copying function from the host system and implements it directly within the storage device controller. The controller performs data migration between LUNs using internal buffers and logic, eliminating the need for host processing resources and network bandwidth while maintaining data transfer capability.
Solution Approach 2:
The storage device controller serves itself by performing data migration operations autonomously. The controller includes dedicated logic to handle ODX Copy Offload instructions, manage LSA block mappings, and execute data transfers between LUNs without requiring external host intervention, thereby reducing overall system resource consumption.
2Productivity
If ODX Offload Copy data migration operations are performed, then data can be migrated between LUNs, but hole formation occurs within LSAs
Solution Approach 1:
The patent converts the potential harm of hole formation into a benefit by implementing a mapping mechanism that tracks LBA locations to LSA blocks. When data is migrated, the system updates the mapping to point the new LBA location to the existing LSA block containing the data, rather than creating a new block. This eliminates holes while maintaining data migration functionality.
Solution Approach 2:
The system implements feedback through its mapping mechanism that continuously tracks the relationship between LBA locations and LSA blocks. During ODX operations, the controller receives feedback about data migration status and adjusts the mapping accordingly, ensuring that LBA locations are properly reassigned to existing LSA blocks to prevent hole formation.
3Adaptability or versatility
If hole formation occurs in LSAs, then data migration is enabled, but host I/O penalties and complexity increase
Solution Approach 1:
The patent introduces an intermediary mapping mechanism between the host and the LSA structure. This mapping layer absorbs the complexity of data migration operations, translating high-level ODX Copy Offload instructions into low-level LSA block management operations. The mapping acts as a buffer that prevents complexity from propagating to the host system.
Solution Approach 2:
The system maintains a copy of the mapping information in the controller's memory, separate from the actual data storage in LSA blocks. This mapping copy allows the controller to efficiently manage data migration by updating references rather than physically moving data or restructuring LSA blocks, thereby reducing host I/O penalties and operational complexity.
Data Source
AI summary
A storage system includes a controller and block-based storage device(s) that include LSA blocks arranged as a log structured array (LSA). The controller creates a first and second LUN, each including LBA locations. The controller assigns the first LUN to a first host and the second LUN to a second host, accumulates first host data associated with a first LBA location of the first LUN, writes a block-size worth of such data to a first LSA block, and maps the first LBA location to the first LSA block. In response to receiving an ODX Copy Offload instruction, the controller determines the first host data should be migrated to a target LBA location in the second LUN, determines the first and second LUN are exclusively mappable to the same LSA, maps the target LBA location to the first LSA block, and unmaps the first LBA location from the first LSA block.