Shadow migration permits automatic data migration from external or internal sources and controls automatic background migration. Regardless of whether the service is enabled or not, data is migrated synchronously for in-band requests. The primary purpose of the service is to allow tuning of the number of threads dedicated to background migration.
NFS mounts on an NFS source are not under the control of the Oracle ZFS Storage Appliance user. Shadow migration mounts cannot be secure; therefore, if the server expects a Kerberos or similar request, the source mount is rejected.