If you are not running a true multi-tenancy environment stay far away from ip spaces, especially in 7-mode.
If the CIFs and NFS are on the same domain, and the same spindles, then what benefit are you getting out of splitting them out.
The only reason to split them out is if you want to invoke a vfiler-dr on separate work loads. For example. App1 and app2, two different RPO's / RTO.
with 7-mode, all volumes must go with vfiler-dr.
Lastly, remember when you configure vfiler-dr, remember to change your snapmirror.conf file b/c they will all default to 0-59/3 * * * - that's every 3 minutes. That's just nuts.
Also, i'm a huge fan of 7-mode, but i made the jump to cDOT recently, with 9.0, and you should start planning this for the future. 7-mode is end of engineering support at this time, plus for cifs no smb 3.
Good luck.!
