A quick post mainly as an excuse to compose some Visio Diagrams...
Transitioning from Data ONTAP Operating in 7-Mode to Clustered Data ONTAP is a - possibly once in a generation - opportunity to restructure your data.
In the below diagrams, we have 4 x NetApp 7-Mode controllers, each physical 7-Mode controller has its pFiler0 and 3 x vFilers, and each pFiler/vFiler has one data IP. We are transitioning/migrating to two newer and more performant controllers running Clustered Data ONTAP.
Option 1: Transition
If we transition from 7DOT to CDOT with pFilers/vFilers to SVMs (Storage Virtual Machines/Vservers) in a 1-1 Relationship, we bring across all the pFilers/vFilers as complete objects, all the data IPs come across as a data LIF, and additionally (a requirement for CDOT 8.3) we need an SVM management LIF per SVM. So, we have 16 x SVMs, 16 x Data LIFs, 16 x SVM Management LIFs, and we’re not going to use any external/on-box load-balancing (since it would increase the number of Data LIFs, but for two nodes that’s not really a problem, if the cluster gets bigger though...)
Image: Option 1 - Transitioning pFilers/vFilers to Clustered Data ONTAP in a 1-1 Relationship
Option 2: Migration (Consolidating Systems)
Assuming there is no business reason for separation of these vFilers, and there are no blockers to their being consolidated (i.e. DFS-N is used to mask CIFS shares, so having shares with the same name is not a problem; name-mappings don’t conflict; all pFilers/vFilers have standard CIFS/NFS/options settings...) Then, in more of a migration that a transition (still using 7 to C SnapMirror though), we can consolidate all these vFilers into one 1 x SVM, 2 x Data LIFs, 1 x SVM Management LIF, and we’ll use external/on-box load-balancing.
It is IMPORTANT to be aware that there is much more effort involved in Option 2 and it will take more time; much more complexity (it’s unlikely even the very latest 7MTT will do exactly what you want if consolidating p/vFilers, leading to adopting a scripted migration solution which is more prone error, and less supportable); and a reduced chance of 100% successful cutover(s) to Clustered Data ONTAP.
Option 1 is the recommended way to go, and of course NetApp wants all migrations to CDOT to be simple and uncomplicated (using the provided 7MTT tool), with the minimum of moving/changing elements, and 100% successful. But, if you’re considering the long-term legacy of migrating to CDOT, and want to simplify your environment further, but understand the risk/complexity/difficulty of migrating/consolidating as per Option 2, and understand that this consolidation would also be difficult enough if it was just 7-Mode to 7-Mode, and you have the skills, then it’s your decision...
Image: Option 2 - Migrating pFilers/vFilers to Clustered Data ONTAP and Consolidating to One SVM