Virtual Port Pause During Live Migration
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Solution Overview
Problem
During live migration of virtual machines in data centers, the process of creating and deleting virtual ports on Fibre Channel switches is time-consuming and error-prone, as it requires tearing down and re-establishing connection sessions, which disrupts data access and increases migration time.
Innovation Solution
Implementing a method to pause and resume virtual ports without tearing down existing sessions, allowing the port to be reassigned between hosts without updating internal Fibre Channel switch data structures, thus maintaining connectivity and reducing the time required for migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual ports are created and deleted on Fibre Channel switches during live migration, then connection sessions can be reestablished for the migrated VM, but the migration process becomes time-consuming and disruptive
Solution Approach 1:
The system performs preliminary actions by creating the virtual port on the Fibre Channel switch before the actual migration occurs. The virtual port is created with a placeholder or dummy World Wide Name (WWN) that allows the connection session to be established in advance. This preliminary port creation eliminates the need to create the port during migration, thereby reducing migration time while maintaining connection validity.
Solution Approach 2:
The system dynamically updates the World Wide Name (WWN) of the virtual port after migration without tearing down the connection session. Instead of deleting and recreating the virtual port, the WWN is updated to reflect the new host's identifier. This dynamic update maintains the continuity of the connection session while adapting to the migrated VM's new identity, thereby reducing migration disruption and time.
2Ease of operation
If virtual ports are bound to specific physical ports on Fibre Channel switches, then data requests can be correctly routed, but the ports cannot be maintained during live migration to different physical ports
Solution Approach 1:
The system segments the binding relationship between virtual ports and physical ports by introducing an intermediate layer of World Wide Names (WWNs). Instead of directly binding the virtual port to the physical port, the virtual port is bound to a WWN, and the physical port is associated with that WWN. This segmentation allows the virtual port to be reassigned to different physical ports through WWN updates without breaking the routing mechanism, thereby maintaining ease of operation while improving adaptability.
Solution Approach 2:
The system uses World Wide Names (WWNs) as an intermediary between virtual ports and physical ports. The WWN acts as a mediator that decouples the direct binding relationship, allowing the virtual port to be reassigned to different physical ports during migration. The Fibre Channel switch uses the WWN to route data requests correctly, regardless of which physical port the VM is connected to, thereby maintaining routing efficiency while enabling port reassignability.
3Reliability
If multiple virtual ports are created and deleted during pre-flight checks and migration, then connection validity can be confirmed, but the process becomes complex and error-prone
Solution Approach 1:
The system performs the connection validity confirmation as a preliminary action during the pre-flight check phase, before migration begins. The virtual port is created and tested for connectivity to the storage LUN during this pre-flight phase. Once validity is confirmed, the port remains active throughout migration, eliminating the need for repeated creation and deletion operations. This reduces complexity while maintaining reliability of connection validation.
Solution Approach 2:
The system maintains the continuity of the virtual port's useful action by keeping it active throughout the migration process rather than deleting and recreating it. The virtual port, once created and validated during pre-flight checks, continues to function during migration with its WWN updated to reflect the new host. This continuous operation eliminates multiple port management operations, reducing complexity and potential errors while maintaining connection validity confirmation.
Data Source
AI summary
In one embodiment, a method includes upon receipt from a first host of a command to pause a virtual port (Vport) associated with a first physical port establishing a connection with the first host, changing a current state of the Vport from an active state to a paused state. The changing of the current state of the Vport to the paused state does not tear down a current session between the Vport and a set of storage disks. The method further includes upon receipt from a second host of a command to resume the Vport at a second physical port establishing a connection with the second host, changing the current state of the Vport from the paused state to the active state and associating the Vport with the second physical port.