IBM V7000 Introduction And Implementation Manual page 322

While data is being copied, IBM Flex System V7000 Storage Node creates a mirror copy
between the source disk at the IBM DS4300 and IBM Flex System V7000 Storage Node.
When the migration process finishes, all you need to do is to Finalize the migration. By
Finalizing the migration, the link between the two mirror copies is broken, and the source
disks at the IBM DS4300 return as unmanaged MDisks to IBM Flex System V7000 Storage
Node (shown in Figure 7-27 on page 305).
Figure 7-23 shows that the disk is in a migration pool that can be reviewed by clicking
Pools  Volumes by Pool. It remains here until the migration process is Finalized.
Figure 7-23 After Migration - Disk is now in a Migration pool
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IBM Flex System V7000 Storage Node Introduction and Implementation Guide