Backup on more than 1 server

How to configure a client to respond to 2 urbackus servers simultaneously

No way except second server configured as Internet backup server.

Not sure about 2 simultaneous backups, however, you could install the client on a server and backup that server to another server.

Search for this title on UrBackup Discourse
“Two UrBackup Server in the Same Net”
or go to

and you will find your answer.