Four-Site Data Replication Transition Without Host Suspension
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Solution Overview
Problem
Existing four-site replication systems require suspension of host operations and compromise data protection during component replacement, as they necessitate suspending hosts to copy data from donor to target systems, which is undesirable for maintaining continuous operation and data integrity.
Innovation Solution
The system enables seamless transition from a donor four-site replication system to a target system by initiating synchronization between local storage systems, allowing hosts to automatically fail over to synchronous storage without suspending operations, using subchannel set switching and asynchronous data replication protocols like SRDF/A, ensuring continuous data protection and availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If host operations are suspended to copy data from donor to target system, then data replication can be completed, but host availability and continuous operation are lost
Solution Approach 1:
The patent establishes preliminary asynchronous replication relationships between the host and target storage system before the transition. The target system proactively receives and stores replicated data in advance, so when the transition occurs, the host can immediately access the pre-replicated data without suspension. This preliminary data preparation resolves the contradiction by ensuring data availability is maintained throughout the transition process.
Solution Approach 2:
The patent introduces an intermediary mechanism where the target storage system acts as a buffer between the donor system and the host. During transition, the host continues to access data through the target system which holds the replicated data, rather than directly suspending host operations. This intermediary approach allows seamless data access while the transition proceeds in the background.
2Manufacturing precision
If host operations are suspended for data copying, then complete data replication is achieved, but operational continuity is compromised
Solution Approach 1:
The patent maintains continuous host operations throughout the transition process by using asynchronous replication. The host continues its I/O operations without interruption while the target system continuously receives and processes replicated data in the background. This continuity eliminates operational interruption time while ensuring complete data replication through the asynchronous process.
Solution Approach 2:
The target storage system performs preliminary data replication in advance using asynchronous protocols, preparing the data before it is needed. This preliminary action ensures that when the host needs to access data during transition, it is already available at the target system, eliminating the need to suspend operations for data copying.
3Reliability
If traditional failover methods are used during transition, then data protection is maintained, but host operation suspension is required
Solution Approach 1:
The patent implements dynamic path switching capabilities that allow the host to automatically transition between donor and target storage systems without suspension. The system dynamically adjusts data access paths during the transition process, maintaining data protection while preserving host operations. This dynamic approach simplifies the transition process compared to static traditional failover methods.
Solution Approach 2:
The target storage system serves as an intermediary that facilitates seamless transition without requiring host suspension. It mediates the data access between the host and the transitioning donor system, maintaining data protection through pre-replicated data while enabling continuous host operations. This intermediary role simplifies the overall transition process.
Data Source
AI summary
Transitioning from using a donor four site replication system to using a target four site replication system includes initiating synchronization between a first local storage system of the donor four site replication system that receives I/O from a host with an alternative first local storage system of the target four site replication system, the host switching to automatically fail over to a synchronous storage system of the target four site replication system that receives synchronous data from the alternative first local storage system following synchronizing the first local storage system with the alternative first local storage system, and the host switching to perform I/O operations with the alternative first local storage system following switching to automatically fail over to the synchronous storage system. The host may run the z/OS operating system. The host may automatically fail over to a storage system by switching subchannel sets.