Virtual Machine Image Write Leasing for Host Fabric
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Solution Overview
Problem
During virtual machine migration, automatic service recovery, or resource configuration changes, there is a risk of multiple instances of the same virtual machine image being written to simultaneously, leading to potential corruption of the virtual machine image.
Innovation Solution
Implementing a lease mechanism that ensures exclusive access to the virtual machine image, where only one entity can write to it at a time, by using a host fabric that reviews and manages requests to instantiate or upgrade virtual machines, and verifies the validity of the lease before allowing changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple virtual machine instances are allowed to access the same virtual machine image simultaneously for migration and recovery operations, then system productivity and service continuity are improved, but the risk of image corruption increases due to concurrent write operations
Solution Approach 1:
The system performs preliminary actions by establishing a lease mechanism before allowing any virtual machine instance to access the virtual machine image. The lease is obtained in advance, ensuring that only one instance can write to the image at any given time, thus preventing corruption while enabling controlled concurrent access for productivity
Solution Approach 2:
The patent introduces a lease mechanism as an intermediary between multiple virtual machine instances and the virtual machine image. This lease acts as a mediator that coordinates access rights, allowing the system to maintain both service continuity through multiple instances and image integrity through controlled access
2Reliability
If a lease mechanism is implemented to ensure exclusive access to the virtual machine image, then image integrity is improved, but system complexity increases due to additional lease management overhead
Solution Approach 1:
The lease mechanism is designed to be self-managing through automatic renewal and expiration. The system continuously renews leases for active virtual machine instances without manual intervention, and automatically revokes leases when instances terminate or migrate. This self-service approach maintains image integrity while minimizing the operational complexity of lease management
3Reliability
If lease renewal is performed continuously to maintain exclusive access during virtual machine operations, then access control reliability is improved, but communication overhead between host and fabric increases
Solution Approach 1:
Instead of continuous lease renewal, the system implements periodic action by renewing leases at specific intervals or events (such as before migration or recovery operations). This approach maintains access control reliability by ensuring leases are valid when needed, while reducing communication overhead by avoiding constant renewal requests
Data Source
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AI summary
A system that includes multiple hosts, each having physical resources, a hypervisor, and a host agent that causes the virtual machines to operate above the hypervisor so as to be abstracted from the physical resources. A host fabric reviews requests to instantiate or upgrade a virtual machine, identifies a corresponding virtual machine image to instantiate the virtual machine from in order to honor the request, and determines whether the virtual machine to be instantiated has a valid lease on the virtual machine image. If the requestor does not have a valid lease, the request is blocked. If the requestor does have a valid lease, the host fabric facilitates the instantiation of the virtual machine from the virtual machine image. This prevents or eliminates the chances of multiple instances of the same virtual machine image writing to the virtual machine image at the same time.