I was wondering how many zones cpanel DNS cluster can handel ? Can we have say 10 servers each hosting 400 domains under dns cluster all syncing zones on all servers?. Now this will create about 6000+ zons on all servers. Will this create load on all servers? Any known problems with such configuration?. Any experience with this kind of configuration?
Now, if the servers config. is ok, and only 400 domains/ server i would say there will be no big issue, and no high load created. Experienced dns clustering before, between 4 server, with over 3000 customers in total, and was handled ok by the servers. The only thing i could suggest will be to chose a nice hour, like in the night to do this, so you will be assured that there will be no much work done on the servers(mail, http queries, etc.)