Distributed Host Copy Migration Using Changed Block Tracking
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Solution Overview
Problem
Existing storage systems face inefficiencies due to prolonged data migration times, which increase the number of writes that need to be processed, leading to additional time and resource usage in synchronizing source and target LUNs.
Innovation Solution
Implementing distributed data migration techniques across multiple host devices in a cluster, where each device handles a portion of the data migration and records writes, reducing overall migration time and the number of writes required, thereby minimizing the iterations needed for synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single host device performs data migration from source LUN to target LUN, then the migration process is simple to manage, but the migration time becomes excessively long and the number of writes to be processed increases significantly
Solution Approach 1:
The patent divides the data migration task into multiple segments by assigning different portions of the source LUN to different host devices in the cluster. Each host device independently migrates its assigned portion, thereby parallelizing the migration process and significantly reducing overall migration time while maintaining manageable complexity through distributed execution.
2Quantity of substance
If migration time is extended, then more data can be migrated, but the number of writes received during migration increases leading to more synchronization iterations
Solution Approach 1:
By segmenting the source LUN into multiple portions and assigning them to different host devices, the patent reduces the time each individual migration task takes. This segmentation directly reduces the window during which writes are received, thereby decreasing the number of synchronization iterations needed and improving overall productivity despite maintaining or increasing total data migration volume.
Solution Approach 2:
The patent enables continuous data migration across multiple host devices simultaneously, maximizing the utilization of available resources. By keeping multiple host devices engaged in migration operations in parallel, the system maintains continuous productive action rather than sequential processing, thereby increasing throughput and reducing the impact of write operations on overall efficiency.
3Loss of time
If multiple host devices are used for distributed data migration, then migration time is reduced and writes are reduced, but the system complexity and coordination overhead increase
Solution Approach 1:
The patent leverages the existing multi-functional capabilities of clustered host devices, which are already configured to service storage devices and handle I/O operations. By utilizing these existing universal functions for the additional purpose of data migration, the system achieves parallel migration without requiring specialized hardware or fundamentally changing device roles, thereby minimizing the increase in system complexity.
Solution Approach 2:
The master host device coordinates the distributed migration by receiving status information from participating host devices and managing the synchronization process. This feedback mechanism allows for centralized coordination of the distributed operations, enabling the system to manage complexity through information flow and control signals rather than requiring complex point-to-point communication between all devices.
Data Source
AI summary
An apparatus in one embodiment comprises a first host device comprising a processor coupled to a memory. The first host device is configured to assign to additional host devices different portions of a source logical unit designated for migration to a target logical unit. In conjunction with migration of the assigned portions of the source logical unit to the target logical unit by the additional host devices, the first host device is configured to receive from the additional host devices respective sets of information each characterizing one or more writes directed to the corresponding assigned portion during the migration. The first host device is further configured to update the target logical unit based at least in part on the received sets of information. In some embodiments, the first host device is configured to assign to itself a portion of the source logical unit designated for migration to the target logical unit.