Hosted nodes: each node's data, history and files are stored in replicated storage that any server can read. When the server running a node fails, the node starts on another server with everything that was saved.
Hosted nodes: a node keeps its encrypted passwords and keys readable wherever it runs, so moving to another server never loses a secret.
Hosted nodes: if a node cannot save its latest changes for more than a couple of seconds, it stops accepting new ones until it can, so a server failure loses at most a moment of work.