Migration across different NAS platform is a challenge for most of the oraganizations. Migration within hardware from same vendor is much easier due to availablility of tools and data replication features within the hardware.
First thing to plan on migration strategy would be -
do you want host level migration to be done or migration at storage level.
Migration at host level can be done by using tools such as robocopy/Xcopy.
But this is time consuming work.
Migration at Storage level.
-is there a common feature within the 2 platforms that you want to migrate to/from. Featured such as NDMP/ or using backups tools.
-is there a tool available in the market that can help migrate NAS data across different vendor hardware.
-is your organization ready to invest in such a tool.
If you are aware Netapp had VFM( virtual file manager) tool which made use of windows DFS ( distribute file system) feature to access/ copy/ migrate data. This tool has been discontinued and I believe the people behind this tool have brought it to market with different name.
The usual way to migrate data at storage level would be segregate your database/ cifs / nfs data. Plan seperate data migrations for eacg set of data.
eg use of data migration features with database ie with microsoft sql, sybase ( sybase ASE) to copy and dump data to new location.
Unix based copy feature/commands for migrating NFS exports and windows based copy/robocopy to copy windows data.
Let us know your findings and experience on this migration.