Amazon FSx for NetApp ONTAP

There is no Block level replication available, you can use AWS DataSync, since you are asking for copy from Fsx Windows to FSx Netapp i assume it is CIFS/SMB filesystem you can use robocopy also. Any file based copy tool will work. Thanks

Hi There

We recommend using AWS DataSync to transfer data between FSx for ONTAP file systems and non-ONTAP file systems, including FSx for Lustre, FSx for OpenZFS, FSx for Windows File Server, Amazon EFS, Amazon S3, and on-premises filers.

See https://docs.aws.amazon.com/fsx/latest/ONTAPGuide/migrate-files-to-fsx-datasync.html