VM Shadow Mode Synchronization for Zero RTO
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current backup systems for virtual machines (VMs) face an unacceptably long Recovery Time Objective (RTO) due to the time required to boot and synchronize the operating system and applications of replica VMs, which can lead to inconsistencies and failures in disaster recovery scenarios.
Innovation Solution
The method involves taking snapshots of the OS disks of source and replica VMs to identify and replicate only the changed blocks, synchronizing the replica VM with the source VM while minimizing downtime and maintaining an acceptable RTO, using techniques such as override updates and snapshot-based synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the replica VM is kept in a powered off shadow mode for protection, then data integrity is maintained, but the Recovery Time Objective (RTO) becomes unacceptably long due to OS boot time and application start time
Solution Approach 1:
The patent applies preliminary action by pre-booting the replica VM OS and pre-loading applications into memory while the VM remains in shadow mode. This allows the OS and applications to be ready in advance, reducing the actual recovery time when failover is needed, while still maintaining data integrity through the shadow mode protection mechanism.
Solution Approach 2:
The patent implements dynamics by creating a hybrid state where the replica VM OS is partially active (booted and loaded into memory) while the VM itself remains in shadow mode. This dynamic state allows simultaneous achievement of fast recovery (through pre-loaded OS and apps) and data integrity (through shadow mode protection), resolving the contradiction between these two requirements.
2Stability of the object's composition
If the replica VM OS is updated to maintain synchronization with the source VM, then data consistency is improved, but the complexity of managing OS updates and synchronizations increases
Solution Approach 1:
The patent uses copying by creating a replica of the source VM OS and maintaining it in shadow mode. The replica OS is initially copied from the source, and updates are applied to the replica in the same manner as the source OS receives updates. This copying approach simplifies update management because the replica can be updated independently while maintaining consistency with the source through the shadow mode mechanism.
Solution Approach 2:
The patent introduces an intermediary mechanism (the shadow mode layer) that mediates between the source VM and the replica VM OS. This intermediary allows updates to be applied to the replica OS without directly affecting the source VM, simplifying the update management process while maintaining data consistency through the mediating shadow mode protection.
Data Source
AI summary
One example method includes powering off a replica VM, taking a snapshot of an OS disk of a source VM associated with the replica VM, taking a snapshot of an OS disk of the replica VM, generating a list of blocks that includes all blocks of the source VM OS disk that have changed since a preceding cloning or snapshot process and further includes all blocks of the replica VM OS disk that have changed since the preceding cloning or snapshot process, and performing an override of the replica VM disk by writing, to the replica VM OS disk, the respective source VM OS disk values for each block in the list of blocks.