how can I migrate data in safe way ? for example on disk1 is more than 75% disk usage and I want to move it on disk2 which have more memory

Do you mean migrating Longhorn volume replicas from one disk to another? You can: 1. Enable the scheduling only for the target disks 2. Scaling up the replica count of the volume to trigger rebuilding in the new disk 3. Wait for the rebuilding complete. 4. Scaling down the count then remove the unwanted replica