Volume Migration uses internal copy services within the VSP One Block architecture to move data from a source volume to a target volume while maintaining host access.
The migration operates in three phases:
- Initialization
The storage system validates the source and target volumes, establishes internal metadata, and prepares the copy relationship.
- Copy operations
Data is transferred in the background using optimized internal copy engines. Host writes are applied to both the source and target volumes to maintain synchronization.
- Cut-over
When the target volume is fully synchronized, the storage system redirects host I/O to the target. The migration relationship is then removed, and the source volume can be re-purposed or decommissioned.
Throughout the operation, the storage system monitors performance and throttles copy activity as needed to protect host workloads.
The following figure shows the data flow during a Volume Migration operation.
There is an upper limit to the number of times a copy operation is executed, and the limit depends on the capacity of the source volume. The limit increases as the capacity of the source volume increases. Theoretically, the source and target volumes can be located anywhere in the storage system, however, there are some restrictions for selecting source and target volumes in migration. For more information about requirements and restrictions when selecting source and target volumes, see System requirements.
After the volumes are fully synchronized (that is, there is no differential data on the source volume), the storage system completes the migration by swapping the Reserve attribute from the target volume to the source volume and redirecting host access to the target volume. The status of the target volume becomes normal. Volume Migration performs all migration operations synchronously (that is, one migration at a time).
The following figure illustrates the state of the volumes after a Volume Migration operation.