azure available set

I have one active directory domain controller ( DCserver) , then I created one available set ( DCserver)  and added another VM (DCserver 1).  however, I found 

- the configuration of DCserver is not synced from DCserver to DCserver1

so I confuse how come this available works . for example , once DCserver is down,

- all traffic ( active directory query) will go to DCserver1 ?

- but DCserver1's configuration is not synced with DCserver, how come it can handle the traffic ?

Thanks,