4550 6.x -> 8.x and standalone->MM

[DonMartin]

I know, there's the migration tool for that purpose.
However, i would like a different approach.

Currently we have a single-controller environment featuring a 4550 controller, running on one of the latest 6.x versions.
As additional information: we're running about 170 APs on it right now (constantly but slowly increasing number).
We recently got to purchase additional controller of the same type, so we finally(!) can approach a redundant solution.

So i'm thinking of trying s.th. the following:
- set up the new controller with a 8.x version
- migrate the config onto the new unit
- move the licenses to the new unit, so that it becomes a 8.x-clone of the old unit (same ip-address, same config - a 1:1 replacement, only with the new sw-release)
- then replace the old unit in the productive network by the new one (so i simply could reconnect the old unit as a recovery plan)
- if that runs fine for a week or so i would factory reset the old unit, upgrade it to the same 8.x-version and add it to form a redundant solution (Mobility-Master based?).


A few questions that come to my mind with this scenario:
- does a version 8.x require the presence of a Mobility Master, or is it still capable of running in standalone-mode?
- judging from the migration guide, the migration tool does not seem to provide the possibility of an "offline"-migration to a different unit to form a clone of the original controller without changing that one?
- since we do not intend to expand the solition beyond these two controllers in future, is it recommendable to upgrade to a version 8.x anyway? Since i don't have to manage multiple controllers what's the point of adding an additional management-plattform (Mobility-Master) which then also has to be maintenanced... just thinking...

[DonMartin]

Since nobody wanted/could answer - here are the answers i derived from the information i got:
- does a version 8.x require the presence of a Mobility Master, or is it still capable of running in standalone-mode?
YES
- judging from the migration guide, the migration tool does not seem to provide the possibility of an "offline"-migration to a different unit to form a clone of the original controller without changing that one?
YES
- since we do not intend to expand the solition beyond these two controllers in future, is it recommendable to upgrade to a version 8.x anyway?
NO

So we will stay with the latest versions 6.x and we are now about to form a redundancy the "oldschool" way