Virtual Machine Live Image Journal Synchronization
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Solution Overview
Problem
Generating consistent backups of virtual machines is complex due to the need for precise synchronization between backup operations and journaling, which can be time-consuming and requires substantial timing coordination, making it difficult to recover data effectively.
Innovation Solution
The system generates live virtual machine images coupled with a journal that logs IO operations, allowing for retrospective synchronization and timing determination, decoupling the backup and journal processes, and enabling recovery at various points in time without requiring tight synchronization between the start of the journal and the backup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If precise synchronization between backup operations and journaling is implemented, then consistency of backup image is improved, but device complexity and timing coordination requirements increase
Solution Approach 1:
The system starts the journal before the backup operation begins, allowing the journal to capture IO operations that occur during the backup process. This preliminary action eliminates the need for complex real-time synchronization between backup and journaling operations, as the journal is already running and recording all relevant IO events that occurred during image creation.
Solution Approach 2:
The journal acts as an intermediary between the backup operation and the IO operations. By introducing this intermediate component that logs all IO events, the system can later correlate backup image data with corresponding IO stream data without requiring direct real-time coordination between backup and journaling processes.
2Measurement precision
If tight synchronization between journal start and backup start is maintained, then timing accuracy is improved, but ease of operation deteriorates
Solution Approach 1:
The journal is started in advance before the backup operation begins, eliminating the need for precise simultaneous startup of both journal and backup. The system only needs to ensure the journal is running before backup starts, which is much easier to implement and operate than coordinating exact simultaneous startup of both processes.
Solution Approach 2:
Instead of requiring the backup to start exactly when the journal starts (synchronization from backup perspective), the approach is inverted: the journal is started first and continues running, then the backup operation begins at any time. This reverses the traditional synchronization model and greatly simplifies operation.
3Reliability
If multiple images are generated to ensure application consistency, then reliability of recovery is improved, but productivity deteriorates
Solution Approach 1:
The journal serves as an intermediary that captures all IO operations during backup creation. This allows the system to generate a single backup image quickly without needing to create multiple images, because the journal provides the missing context information about IO operations that occurred during image creation, enabling later determination of application consistency.
Solution Approach 2:
The journal automatically records all IO operations without requiring manual intervention or multiple backup passes. This self-logging capability provides the necessary information to assess application consistency from a single backup image, eliminating the need to generate multiple images to ensure recovery capability.
Data Source
AI summary
A live image of a virtual machine is disclosed. When generating a live image, an image of a virtual machine is generated. A journal is also generated that starts before a start time of the image and ends after the start time of the image. A live image is then generated by synchronizing the start time of the image with the journal. This includes evaluating or analyzing the journal relative to the backup to determine or synchronize the start time relative to the entries in the journal.