Although the Tenant Storage Migration Wizard allows you to set up storage migrations for multiple tenants, the system limits the number of individual storage-consuming items (VMs, vApp templates, catalog items, and so on) that are migrated in parallel to avoid overloading vCenter or exceeding the vCenter limits on concurrent storage migrations. In the default configuration, the system configuration property vcloud.concurrentTenantStorageMigrationLimit is set to a value of 4, so that no more than four items are migrated in parallel.
You can use the cell-management-tool manage-config subcommand to change this value. vSphere imposes a hard limit of eight parallel storage vMotions, so setting vcloud.concurrentTenantStorageMigrationLimit to a value greater than 8 is equivalent to setting it to a value of 8.
You can use the Tenant Migration tab of the Cloud Director Web Console Logs page to view the status of queued or in-progress migrations, and to cancel an in-progress migration.
At least one target datastore must be accessible to the ESXi host running the migrated VM.