Hash-Based Xcopy Synchronous Replication Optimization
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Solution Overview
Problem
Synchronous replication systems face challenges in efficiently supporting xcopy commands due to potential out-of-sync conditions between source and target storage systems, leading to increased data transfer times and complexity.
Innovation Solution
Implementing a hash-based mechanism that checks for the existence of short hash handles and full digests at the target site, optimizing data transfer by sending short hash handles first to determine if the full digest or data page needs to be sent, and incrementing reference counters when both source and target LUs are actively synced to the same target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional synchronous replication is used to handle xcopy commands, then data consistency between source and target systems is maintained, but data transfer time and system complexity increase
Solution Approach 1:
The system performs preliminary actions by checking if the target LU is already in active synchronous replication with the source LU before executing xcopy. This pre-check determines whether optimization can be applied, avoiding unnecessary data transfer when the target is already synchronized
Solution Approach 2:
The invention extracts and utilizes the replication state information from the target system to optimize xcopy operations. By checking the replication state separately from the xcopy execution, the system can make informed decisions about data transfer requirements
2Reliability
If traditional synchronous replication is used to handle xcopy commands, then data consistency between source and target systems is maintained, but system complexity increases
Solution Approach 1:
The target system provides self-service by maintaining and exposing its own replication state information. When an xcopy command arrives, the target system autonomously determines whether it is already synchronized with the source, eliminating the need for complex coordination protocols between source and target
Data Source
AI summary
In one aspect, support for hash based xcopy replication for synchronous replication is provided. An aspect includes determining, in response to an xcopy command, whether a source logical unit (LU) and a target LU are in active synchronous replication to the same target site. Upon determining that the LUs are in active synchronous replication, increasing a count of a hash handle list, obtaining a unique full hash digest, and sending the digest with volume replication pairing identifier, offset, and length to the target. Upon receiving a request from the source, searching, by the target, for local hash handles of the digest; and upon determining the local hash handles exist in the digest, incrementing, the reference counter handle list, and sending corresponding hash handles from the source site to the target.