If your source has 2 vfilers and that configuration works now, just transition to 2 SVMs. One for the old vfiler1, one for the old vfiler2.
If your source is a single vfiler, then after cutover make sure the CIFS path is first in the home directory search list.
Configure your transition project to keep the 7mode mount paths. Inspect the clients that fall into this use case and determine what mechanism they use for finding their home directories in the current state. Understanding how it works now is key to making it work after transition.
Include a test for this scenario in your transition pilot project to verify the correct client mounts the correct home directory post cutover, and be sure to document any post-cutover steps that need to be performed to configure home directory behaviour in your environment.
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