Hi Li Li
Thanks for your quick answer.
Currently I don't need considering HA configuration of DB. However, I need at least three nodes of zookeeper and I want to set up the zookeeper node on DB Server to physically distribute the ZK node. Is there a problem with this configuration? Customers want to have a minimum number of servers.
ZooKeeper is used to electe new leader. On ThingWorx HA, it was used to elect new ThingWorx server. Usually ZooKeeper's number should be 2n+1, so that it can tolerate n server down. It means if you have 3 ThingWorx servers and with 3 ZooKeepers, you can have one ThingWorx server down without letting end user knowing that. If you only have 2 ThingWorx servers and 2 Zookeeper's, the election function is meaningless.
Although there is no offical article said we have to set up 3 ThingWorx servers for HA, it seems the minimum number of ThingWorx server should be 3.