Storage Control System Batching Writes for Remote Copy Consistency
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Solution Overview
Problem
Existing methods for maintaining consistency in asynchronous remote copy facilities face challenges such as high resource usage, performance degradation, and increased Recovery Point Objective due to frequent snapshot requirements or sequential write processing, which are inefficient and not scalable for multi-node systems.
Innovation Solution
A storage control system that batches writes based on independence criteria, assigns sequence numbers concurrently, and transmits batches to the secondary for processing, allowing concurrent execution and reducing inter-node messaging, thereby optimizing resource use and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sequential write processing is used to maintain consistency, then data consistency is preserved, but system performance and productivity deteriorate
Solution Approach 1:
The patent segments writes into batches that are processed concurrently rather than sequentially. Each batch is assigned a sequence number and processed independently, allowing multiple batches to be handled in parallel while maintaining consistency through the sequence number ordering mechanism.
Solution Approach 2:
The patent performs preliminary actions by assigning sequence numbers to batches before processing. This allows the system to pre-establish the ordering relationship between batches, enabling concurrent processing while ensuring that writes are applied in the correct sequence to maintain consistency.
2Reliability
If frequent snapshots are taken to maintain consistency, then data consistency is preserved, but resource usage and device complexity increase
Solution Approach 1:
The patent extracts the snapshot function from the consistency maintenance mechanism. Instead of relying on snapshots to ensure consistency, the system uses sequence numbers assigned to batches, eliminating the need for frequent snapshot operations and reducing associated resource overhead.
Solution Approach 2:
The patent replaces the snapshot copying mechanism with a sequence number-based ordering system. Rather than creating and managing snapshot copies of data to ensure consistency, the system uses lightweight sequence number metadata to control the order of write application.
3Reliability
If sequence numbers are assigned to every single write, then data consistency is preserved, but messaging overhead and device complexity increase
Solution Approach 1:
The patent merges multiple individual writes into batches, assigning a single sequence number to each batch rather than to every individual write. This reduces the number of sequence number assignments and associated messaging overhead while maintaining consistency through batch-level ordering.
4Reliability
If colours are formed at regular intervals to maintain consistency, then data consistency is preserved, but Recovery Point Objective increases
Solution Approach 1:
The patent performs preliminary sequence number assignment to batches before they are processed and transmitted to the secondary system. This allows the primary system to maintain an updated view of the consistent state, reducing the Recovery Point Objective by having consistency information prepared in advance rather than waiting for colour formation intervals.
Data Source
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AI summary
A storage control system adapted to operate as a remote copy pair by communicating between a primary and a secondary of the remote copy pair comprises: a selector for selecting writes to be placed in a batch based on one or more criteria; a sequence number requester for requesting a sequence number for the batch; a sequence number granter for granting a sequence number for the batch; a batch transmitter for transmitting the batch to the secondary; a permission receiver for receiving a permission to write the batch from the secondary; and a write component responsive to the permission receiver to write the batch to completion; wherein the secondary is responsive to the completion to grant a further permission to write for a further batch.