The cutover phase is the final phase of the volume move. During the cutover phase, the data in the source volume and the destination volume is synchronized. I/O operations are redirected to the destination volume and the volume move is complete.
The following processes take place during the cutover phase.
- All LUNs in the source volume are in a suspended I/O (quiesced) state. The quiesced state empties the LUNs of pending I/Os and prevents new I/Os from being scheduled. Any new I/O post-LUN quiesce is simply dropped and no response is sent to the initiator.
- The source volume is quiesced. The volume quiesce fails new commands on the volume with busy status and drains pending commands on the volume. As part of the quiesce operation, WAFL captures the final delta lag in a Snapshot copy, which is named according to the convention ndvm_final_<timestamp>.
- The destination volume is then synchronized completely with the source volume with the delta from ndvm_final_<timestamp>. This is the last SnapMirror update between the two volumes before servicing the I/O from the destination volume.
- The identities of the source volume and the destination volume are swapped.
- The migrated volume is brought online with the identity of the original source volume and the LUNs are unquiesced, at which point they are in a mapped state and ready to accept I/O.
- The source volume is deleted, unless the user specified retaining it. The volume can be retained using the vol move -k command. If the source volume it retained, the vol move operation will rename it as <source volume name>_old_<timestamp>.
- The ndvm_final_<timestamp> Snapshot copy is retained in the moved volume at the destination. However, once cutover is complete, you can delete it.
Note: The host application might encounter I/O disruptions if storage system reboot, nondisruptive upgrade (NDU), shutdown, takeover, or giveback occurs during the volume move.
If the volume move is not completed within the specified cutover period (default 60 seconds), then the cutover phase is timed out, logging the appropriate error messages, and the volume move reverts to the data copy phase.
If the cutover phase is successful, it results in the following:
- The contents of the destination volume are identical to the source volume.
- The destination volume takes the identity of the source volume.
- After the volume is moved, the LUN at the destination starts processing I/O operations.
Depending on the number of cutover attempts, the volume move tries to enter the cutover phase again. If cutover is not completed within the specified number of cutover attempts, then the volume move is paused and an appropriate error message is recorded in the log file. You can then manually resume the volume move.