If you power off and on the external storage system when the local storage system is on, the following Universal Volume Manager operation is required.
Disconnect External Storage Systems: Run this command before you perform maintenance on an external storage system or perform a scheduled shutdown. When Disconnect External Storage Systems is selected, the I/O response from hosts of external volumes mapped as a local storage system volumes will stop. Next, data for each external volume is destaged from the cache memory of the local storage system to the external volume.
Reconnect External Storage Systems: Run this command to determine whether the defined configuration information of external volumes mapped as local storage system volumes matches the status of the external volumes. If external volumes can be used as mapped volumes, I/O to the external volumes is accepted, and the volumes can be used again.
The Reconnect External Storage Systems command is used to recover from an I/O failure after the Disconnect External Storage Systems command has been run.
If there are any path issues, they must be resolved before you run this command.
When you run the Reconnect External Storage Systems or Reconnect External Volumes command, if external volumes can be used, I/O to the external volumes is accepted and the volumes can be used again. If an external volume cannot be used, its status is Blockade.