Till, thanks for your response.
ok, i am know.
little other questions.
my idea be to change the master server, but not the tasks running on servers
ok, new i am make server4.domain.ltd and configure him that new master.
step 1. from server 1domain.ltd migrate dbispconfig on server4.domain.ltd
step 2. for all sleve servers change master (from server1.domain.ltd > server4.domain.ltd)
I think it is posible. servers 2 , 3 must be work for server 4 new correctly.
on ispconfig on server1.domain.ltd run php -q install.php - select expert, select new master is server4.domain.ltd , select reconfigure all tasks - end......... but! all data , postfix, sql, apache , mailbox working continually from server1.domain.ltd , or this operation is delete or wrong data and server is emty new?
sorry for my pure english