Container Cluster Migration Using Direct PV Sync Across Storage Backends
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Solution Overview
Problem
Existing methods for migrating stateful workloads between container clusters with different storage backends are insecure, time-consuming, costly, and can cause inconsistencies due to the use of intermediary repositories, especially when dealing with large persistent volumes.
Innovation Solution
Implementing a migration process that creates PV transfer pods on both source and destination clusters to directly synchronize data between storage backends using secure protocols, minimizing the need for intermediary repositories and ensuring data consistency through a two-stage synchronization approach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backup-and-restore tools run as long-lived privileged processes to copy persistent volume data, then data migration can be performed, but security concerns arise because such processes can be compromised to mount denial-of-service attacks or leak confidential data
Solution Approach 1:
The patent uses short-lived migration pods instead of long-lived privileged processes. These pods are created temporarily to perform the data migration task and then terminated, eliminating the security vulnerability of persistent privileged processes while maintaining the capability to migrate persistent volume data between storage backends
2Reliability
If persistent volume data is copied to an intermediary repository, then data can be transferred between storage backends, but migration time increases significantly and the cost of provisioning the repository is high
Solution Approach 1:
The patent extracts and eliminates the intermediary repository from the migration architecture. Instead of copying data through an external repository, the solution enables direct data synchronization between the source and destination storage backends, removing the time-consuming intermediate storage step and reducing provisioning costs
3Productivity
If the workload continues accepting requests at the source cluster while migration is in progress, then downtime is reduced, but inconsistencies arise between the states of source and destination clusters
Solution Approach 1:
The patent implements a two-stage migration process where the first stage performs incremental synchronization while the workload remains active, and the second stage performs a final consistency check and cutover. This preliminary action ensures data consistency is verified before completing the migration, resolving the contradiction between maintaining availability and ensuring consistency
4Quantity of substance
If an intermediary repository is used as backup location, then data can be stored during migration, but it becomes a performance and scalability bottleneck if multiple workload migrations need to be performed in parallel
Solution Approach 1:
The patent segments the migration architecture by eliminating the centralized intermediary repository and enabling direct peer-to-peer data synchronization between source and destination clusters. This segmentation allows multiple migration operations to run in parallel without competing for repository resources, thereby removing the bottleneck and improving overall migration throughput
Data Source
AI summary
Techniques for migrating a stateful workload between a source container cluster and a destination container cluster that have different storage backends are provided. In one set of embodiments, these techniques involve creating and running, at the time of the migration, transfer processes in the source and destination container clusters respectively, where (1) the source-side transfer process mounts the workload's persistent volumes (referred to as source persistent volumes) in the source container cluster, and (2) the destination-side transfer process mounts destination persistent volumes that have been dynamically provisioned in the destination container cluster in accordance with the specifications of the source persistent volumes. Upon being created and run, the source-side and destination-side transfer processes can work in concert to securely copy the data in the source persistent volumes to their corresponding destination persistent volumes, thereby transferring that data between the storage backends of the source and destination container clusters.