In my understanding this means that the IP 172.30.1.50 is fully trusted and every Unix-User coming from this IP is mapped to the Domain-Administrator. Well, it works for the root-Account, but not for any other user:
[root@linux mnt]# mount -t nfs netapp:/vol/vol_data/folder /mnt/mountpoint
[root@linux mnt]# ls -la
drwxr-xr-x. 6 root root 4096 31. Jan 14:31 .
dr-xr-xr-x. 23 root root 4096 21. Feb 12:51 ..
drwxrwxrwx 3 root root 4096 21. Feb 13:57 mountpoint
[root@linux mnt]# ls -la mountpoint/
drwxrwxrwx 3 root root 4096 21. Feb 13:57 .
drwxr-xr-x. 6 root root 4096 31. Jan 14:31 ..
drwxrwxrwx 12 root root 4096 21. Feb 14:00 .snapshot
[root@linux mnt]# su user
[user@linux mnt]# ls -la mountpoint/
ls: failed to open dir: Permission denied
I'm pretty new to Netapp so i'm thankful for every help.
I am not so sure about few things that you were trying...
As you have said you have problem mounting an *NFS* share on a *nix machine i would assume its based on complete NFS options and not cifs. usermap.cfg is for cifs if you ask me. And NFS doesn't get attached to any domain at all(unless you use nfs4) and it uses ip based authentication unlike cifs which is user based authentication were domain come in to picture.
If I can let you suggest here would be my suggestion:
1) To fix the current issue
What is the export option for the volume "/vol/vol_data/"
if it has anything apart from the one that you have for "/vol/vol_data/folder -sec=sys,rw=172.30.1.40,root=172.30.1.40" then add this network as well.
2) Create a new qtree "qtree create /vol/vol_data/folder"
Change the qtree security to unix and try to export it again and mount on the machine and check.
For user mapping to work user must be known to NetApp. Meaning - either it has to be entered in local /etc/passwd or NetApp must be using network based user database (e.g. LDAP). root is usually present in /etc/passwd so it works. Any other user is likely missing so it fails.
For test you can add non-root user from your workstation to /etc/passwd on NetApp. Be sure to use the same UID.