[CentOS] how do i have a clone centos server

Dear All,

I do have a centos 5 srver running the following. the server is a dell pc with standard config

1 gb ram 120 gb ide hdd 3.2 ghz cpu NIC

Mail server Dns Server webmail Mailscanner

now i would like to have another server like mirroring this server .. so incase there is any problem with this server the other server is always online and the problem server could be fixed without our users gettin affected

apprecite if anybody can help giving some clues or is there any software avaliable. also is the hardware in both servers have to be identical or it can be different

thnks n regards

simon