Write Tracker Data Copying for Non-Disruptive Storage Migration
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Solution Overview
Problem
Existing data transfer methods between storage systems often require suspending host access for extended periods, which is unacceptable and can disrupt disaster recovery systems, especially when dealing with large data sets.
Innovation Solution
Implementing a system that resets a write tracker on the source storage system to track writes from host computing systems, allowing data copying to occur without suspending writes, and using job control language to manage data transfer, ensuring minimal disruption by repeatedly copying data portions until an end condition is met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is copied from source storage system to target storage system using batch copy operation, then data copying reliability is improved, but host access suspension time increases
Solution Approach 1:
The system performs preliminary actions by setting up write tracking before the copy operation begins, and by pre-identifying data blocks that need to be copied. This allows the actual copy operation to proceed more efficiently once host access is suspended, reducing the overall suspension time while maintaining reliability.
Solution Approach 2:
The system implements feedback mechanisms through write trackers that monitor and record all write operations to the source storage system. This feedback information is used to identify which data blocks have changed and need to be copied, allowing the system to optimize the copy operation by only transferring necessary data rather than copying entire datasets, thus reducing suspension time.
2Ease of operation
If non-disruptive data copying is implemented allowing host access during copy operation, then host access continuity is improved, but system complexity and error susceptibility increase
Solution Approach 1:
The patent introduces write trackers as intermediary components that mediate between the host storage system and the data copying process. These trackers intercept and monitor write operations, providing a simplified interface that allows non-disruptive copying without requiring complex coordination between multiple systems. The intermediary manages the complexity internally while presenting a simple operation to users.
3Ease of operation
If non-disruptive data copying is implemented allowing host access during copy operation, then host access continuity is improved, but data consistency and disaster recovery reliability worsen
Solution Approach 1:
Write trackers provide continuous feedback about all write operations to the source storage system. This feedback mechanism ensures that the system has accurate, up-to-date information about which data blocks have been modified, allowing it to maintain data consistency even while hosts continue to access the storage system during the copy operation. This feedback is crucial for ensuring disaster recovery reliability.
Solution Approach 2:
The patent replaces mechanical suspension of host access with a software-based tracking and coordination system. Instead of physically stopping write operations, the system uses write trackers to monitor and record changes, then uses this information to manage the copy operation. This substitution allows host access to continue while maintaining data consistency through information-based control rather than mechanical interruption.
4Manufacturing precision
If write tracking is implemented to monitor data changes during copy operation, then data copying accuracy is improved, but processing overhead increases
Solution Approach 1:
The system extracts only the essential information needed for accurate copying by using write trackers to monitor and record specifically the write operations and their locations. Rather than tracking or copying all data movements, the system extracts only the critical change information, reducing processing overhead while maintaining copying accuracy. This selective extraction focuses resources on what is truly necessary.
Data Source
AI summary
Copying data from a source storage system to a target storage system includes resetting a write tracker on the source storage system to track writes to the source storage system by one or more host computing systems, copying data from the source storage system to the target storage system after resetting the write tracker, suspending writes to the source storage system after copying the data, and copying data portions of the source storage system to the target storage system that are indicated as being written by the write tracker after suspending writes to the source storage system. Applications that write data to the source storage system may be quiesced in connection with suspending writes to the source storage system. Data portions may be repeatedly copied from the source storage system to the target storage system until an end condition is reached.