Learn about ONTAP Foreign LUN Import
Suggest changes
PDFs
Foreign LUN Import (FLI) is an ONTAP capability that enables block level (LUN) data migration by copying user data from a foreign array LUN into an ONTAP LUN. ONTAP performs the migration by acting as a SCSI initiator that reads from the foreign LUN and writes to the destination ONTAP LUN.
FLI operates strictly at the LUN level and is intended for SAN migrations; it is not a file-level migration tool (NAS/file protocol migrations such as NFS/SMB require different approaches). FLI supports both offline and online migrations. In offline mode, host I/O is stopped for the duration of the import; in online mode, host operations resume after a short cutover while the import continues in the background.
Foreign LUNs appear in the ONTAP storage stack and must be explicitly marked as foreign to prevent accidental overwrite/ownership. FC FLI used FC backend connectivity (initiator ports, zoning/masking), while iSCSI FLI, the backend uses a iSCSI software initiator bound to intercluster connectivity, while the host-facing (frontend) protocol after migration can still be FC or iSCSI depending on design.
The following summarizes the key differences between the offline and online migration approaches.
| Area | Offline FLI | Online FLI |
|---|---|---|
Host I/O during import |
Host I/O is stopped for the full import duration. |
Host I/O can run while the import copy continues (after cutover). |
Downtime profile |
Requires downtime throughout the import window. |
Designed to be mostly non-disruptive, typically requiring only a short outage for cutover. |
Operational use case |
Best when longer downtime is acceptable or required by the application or host model. |
Best when downtime must be minimized and you can tolerate background copy activity. |
In the offline workflow, the host is disconnected for the entire duration of the import.
In the online workflow, the host is disconnected only for a short cutover period while the import transitions from copying to completion.
