I recently had to do the titular task on ONTAP 9.9.1. A fairly simple piece of work, but worth recording a few notes.
|AFF C190 Connectivity Options|
i) Enterprise Laptop Challenges
Firstly, I like to use HFS.exe to serve software over HTTP because it's just so simple to use, but I was having challenges with my Enterprise Laptop security.
i-1) The first thing was that I had to run this in PowerShell (thanks to Samtoh Hewti for pointing this out):
Set-NetConnectionProfile -Name "Unidentified network" -NetworkCategory Private
Note i: The laptop to device management port (switch/storage array) should come up as "Unidentified network", but check the output of the first command first.
Note ii: Doesn't matter if your laptop has builtin RJ-45 socket or you're using a USB RJ-45 dongle, have to do the same thing every time you reconnect the ethernet cable.
i-2) I am allowed to create rules in 'Windows Defender Firewall with Advanced Security' but I could not get a rule specifically for hfs.exe to work. Fortunately, I can create a rule:
- What type of rule would you like to create? Program
- Does this rule apply to all programs or a specific program? All programs
- What action should be taken when a connection matches the specified conditions? Allow the connection
- When does this rule apply? Domain + Private + Public
- Verify bill-of-materials (SO) is as expected and required
- Verify new destination capacity
- Verify connectivity of new system
- Understand workloads to be migrated
- Require config workbook for new AFF nodes.
- Acquire any software needed (like ONTAP, switch OS, switch RCF)
- Acquire licenses for new nodes (usually come pre-loaded, but always good to have them to hand)
1) The Plan
This is the plan followed:
- Update switches (2x BES-53248 switches were used as temporary cluster switches)
- Convert cluster from switchless to switched - see 
- Initialize AFF C190 with 9.9.1Px to match cluster
- Join AFF C190 to cluster
- Configure networking (inc. LACP interface groups) etcetera
- Create data aggregates
- Test network reachability from C190s, ideally including creation of test SVM, test LIFs and verification of comms from clients
- Vol move SVMs and data from FAS to AFF C190 nodes - see 
- Decommission FAS nodes - see 
- Convert cluster from switched to switchless - see 
- And repeat for the other cluster.
docs.netapp.com is very good these days. If I'm working on a customer site, I often intentionally follow the official documentation to cover myself (i.e. if something goes wrong, and my understanding is not at fault, the issue is with the documentation.) Below are some titles of documents I used. Rather than using the links below I'd suggest simply googling them to find the latest version.
-  Migrate to a switched NetApp cluster environment (with BES-53248 switches)
-  volume move start
- We used the -cutover-action wait to seed vol moves overnight and cutover in the morning. Every required volume type - including all SVM-DR vols, MDV vols (requires set -priv adv) - was moved non-disruptively with vol move start.
-  How to remove an LS mirror relationship
-  Create and initializing load-sharing mirror relationships
-  Remove nodes from the cluster
-  Migrate to two-node switchless cluster with NVIDIA SN2100 cluster switches (there was no document for BES-53248 when I checked and I have reported this)
Note: Intercluster LIFs can also be migrated with net int migrate. For all snapmirror functions to work 100%, each node in the cluster should have an intercluster LIF.
2 x FAS HA-pairs (sort of prod and DR) each with around 7TB data, took 3 days to migrate to 2 x AFF C190 HA-pairs.
- 1st day was setting up the 1st AFF C190 and commencing vol moves.
- 2nd day completing vol moves to 1st AFF C190 and setting up the 2nd AFF C190.
- 3rd day completing vol moves to 2nd AFF C190 and any decommission tasks.