you can do it in many ways depending upon the type of data:
If it is block level data (exchange, sql, sharepoint luns), use the host level or application level replicate or copy. you can also use the DTA, a device which is a paid services from netapp.
If it is file level data migration, use the 7MTT tools or use the secure copy or robocopy or any copy tools
Both needs download time, when you do a cut-over to c-mode
thank you,
AK G