[Samba] How to add a second Samba DC to create homogeneous multi-DC domain?

[mail at crcomp.net]

Greetings,

For sake of failover it's time for me to add a second samba DC to a
domain with a single samba DC. At present, there's only one samba DC.
There are no Windows DCs.

The documentation seems a little dated:

  https://wiki.samba.org/index.php/Samba_4.0_Whitepaper

Apparently a SysVol replication workaround must be implemented:

  https://wiki.samba.org/index.php/Bidirectional_Rsync/Unison_based_SysVol_replication_workaround 

Does only one server at a time own the FSMO roles?

Is it OK for the new DC to use 4.5 if the existing DC uses 4.1?

What's missing? Are there any other things to consider?

Thank you,

-- 
Don Kuenz KB7RPU

Genius is nothing but a greater aptitude for patience. - de Buffon