Parallel I/O Director Replication for FICON Emulation
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Solution Overview
Problem
Synchronous data copying from a local storage device to a remote storage device introduces significant delays due to data conversion and transfer processing, which affects write operation acknowledgments.
Innovation Solution
The system employs two directors within the local storage device to mirror incoming data independently, allowing one director to handle local processing while the other director transfers data to the remote storage device using RDF or FICON initiator emulation, enabling parallel data handling and acknowledgment synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is synchronously copied from local storage device to remote storage device, then data protection and availability are improved, but write operation delay increases significantly
Solution Approach 1:
The storage device is divided into multiple independent directors (first director for local processing, second director for remote replication) that can process data simultaneously. This segmentation allows the local write operation and remote data copy operation to proceed in parallel, reducing the write delay while maintaining synchronous replication for data protection.
Solution Approach 2:
The patent introduces an independent inter-director link that creates a separate data transmission path between directors, independent of the host-storage bus. This dimensional separation allows data to be mirrored between directors without blocking the host-write path, enabling concurrent operations.
2Adaptability or versatility
If data is converted to internal format and reformatted for remote transfer, then data compatibility is improved, but processing time and delay increase
Solution Approach 1:
The first director receives data from the host in its original format and immediately mirrors it to the second director before any conversion or processing occurs. This preliminary action ensures the original data format is preserved and avoids time-consuming conversion operations during the critical write path.
Solution Approach 2:
Instead of converting and reformating data sequentially, the system creates a direct copy of the incoming data from the first director to the second director. This copying approach maintains data integrity while eliminating the time-consuming format conversion steps that would otherwise be required.
3Productivity
If data is moved through multiple components within local storage device, then data processing capability is improved, but transfer delay increases
Solution Approach 1:
The patent extracts the data mirroring function from the main data processing path by introducing a dedicated inter-director link. This separation removes the bottleneck of moving data through multiple internal components (global memory, RDF director, etc.) and allows direct parallel processing at the director level.
Solution Approach 2:
The independent inter-director link acts as an intermediary channel that enables direct data sharing between the first and second directors without routing through the host bus or other storage components. This intermediary path eliminates the delay of moving data through multiple processing stages.
Data Source
AI summary
Replicating data written to a local storage device from a host includes receiving the incoming data using a first director that mirrors the incoming data from the first director to a second director independently of any links that transmit data to or from the directors and other components of the local storage device and transmitting the mirrored data from the local storage device to a remote storage device. The first director may be a target device (e.g., FICON target) that accepts data and connection requests from the host. The second director may be an initiator device (e.g., FICON initiator) that provides data and connection requests to the remote storage device. The second director may emulate a FICON initiator. The local storage device may wait for an acknowledgement of receipt of the data from the remote storage device before acknowledging receipt to the host.