I'm working through this exact issue right now with Netapp support. I know the answer has to do with how LDAP is configured on the Netapp, but we just haven't gotten it working yet. As soon as we get it configured correctly, I'll come back and post how we did it. If you figured it out already, please give an update.
If Linux servers are already been authenticated by AD, why would you need name-mapping? Once you configure CIFS server AD DC is added as an LDAP server to the Vserver and LDAP schema configuration is setup automatically.
What is the challenge here and Is there something I am missing here?
The issue is that Winbind generates a UID based one a Windows SID from a user and Netapp doesn't know how to translate that. On my Netapp, I can setup an NTFS qtree and give myself permissions and that works great in Windows. I can mount that qtree to a Linux machine via NFS. I turn on "cifs_trace.login" and from the Linux system CD into the mounted qtree directory and receive a permission denied immediately. Looking at the console it outputs and error that it doesn't know what the UID is.