Dynamic Consistency Groups for Virtual Machine Data Replication
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Solution Overview
Problem
Existing storage replication techniques, such as array-based and host-based replication, are limited in defining consistency groups, which restricts the flexibility and scalability of ensuring crash-consistent replication across multiple storage devices, particularly for virtual computing instances.
Innovation Solution
The implementation of a virtualization management module that manages consistency groups dynamically, allowing any number of groups to be defined, and performs periodic replication of storage volumes to maintain write order consistency, using APIs to prepare, create, and manage replica virtual volumes across sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional consistency groups are used for storage replication, then crash-consistent replication is achieved, but the number of groups is limited to tens of groups
Solution Approach 1:
The patent segments the consistency group management by introducing a virtualization layer that separates storage consistency management from physical storage devices. Each virtual machine can have its own consistency group independently managed by the virtualization system, allowing unlimited groups rather than being limited to tens of groups at the physical storage level.
Solution Approach 2:
The virtualization management module acts as an intermediary between storage devices and virtual machines. It manages consistency groups dynamically, allowing any number of consistency groups to be defined by the virtualization system rather than being constrained by physical storage array limitations.
2Reliability
If consistency groups are defined upfront, then replication consistency is ensured, but extensive upfront effort is required
Solution Approach 1:
The patent transforms consistency group definitions from static upfront configuration to dynamic on-demand creation. The virtualization management module can create consistency groups dynamically based on virtual machine requirements, eliminating the need for extensive upfront setup effort while maintaining replication consistency.
Solution Approach 2:
The system changes the parameter of consistency group creation from requiring upfront definition to allowing dynamic definition. The virtualization management module can define consistency groups on-demand based on virtual machine provisioning needs, reducing setup time while ensuring replication consistency.
3Ease of manufacture
If storage-based replication is used, then replication is managed directly between storage systems, but flexibility is limited
Solution Approach 1:
The patent adds a virtualization dimension to storage replication. Instead of managing replication directly at the physical storage array level, the virtualization management module introduces a virtual layer that manages consistency groups for virtual machines, providing greater flexibility and scalability while maintaining ease of replication management.
Data Source
AI summary
Virtual computing instance data that are stored across multiple storage volumes are replicated in a manner such that the write order is maintained. The frequency of the replication is set so that the recovery point objective defined for the VM data can be satisfied. The replication includes the steps of determining a set of logical storage volumes across which the virtual computing instance issues dependent write IOs, issuing a first command to the virtual computing instance to block new IOs and to block receipt of IO acknowledgements, issuing a command to create replicas of all the logical storage volumes in the set, and then issuing a second command to the virtual computing instance to unblock new IOs and unblock receipt of IO acknowledgements.