To prepare the Analytics to add external data
Navigate to the System > Settings.
For migration preparation process, the Settings page will display a DATA MIGRATION section. If the DATA MIGRATION section displays an error that the DATA MIGRATION IS DISABLED, then expand the existing hard disk size to 2x times the current hard disk size available. Refer Expanding Existing Disk.
Click Prepare to start the process to allow the existing Analytics to support external disk addition. On prompting for confirmation click OK.
This process will take some time to complete. Refresh the page at regular intervals.