This is not practical for a home setup. Not because it would be expensive for more hardware or whatever, but because as soon as you have multiple systems doing the same thing, their state diverges and for pretty much anything that is popular for selfhosting you cannot merge them again or mirgrate users between them without loosing anything. Distributed databases alone are a huge pita, and maintaining such redundant setups would be a million times more effort than just making sure that you can easily and quickly atomically roll back failed updates