[CentOS] server mirroring how to

Dear All,

I have the following setup which is the heart of our organistion and runs
the following for a long time

Centos 5.0 server which is used as a

Primary Mailserver  running sendmail about 400 users
mailScanner
Primary DNS server using bind
Webserver running apache
squirrel mail  web server

i also do have a another centos secondary DNS server and same machine used
as my secondary mail server with no mail users

Currently i have been following a little crude way of backup
i shut down the Primary machine and I use clone Gozilla to make a
duplicate of the original disk and keep it standby

i do it weekly basis which is really a crude way

i am jus googling arround for a solution in where i could have online
mirroring of another machine

i could have an identical hardware machine which could be running online
so if the first machine fails the second one is avaliable instantly

also if i create a new user or a new mail user ther user is replicated on
both machine

if i upgraded or install any software on one machine it is replicated on
the other automaticalu..
so we have total redundancy

can it be done

i was googling arround and actually found linux heartbeat but could not
really get the hang of it.
to my understanding heartbeat works on service which one would like to
mirror but for me i would like disk mirroring on different servers

any body has done the above
apprecite your advice and help


 regards

fabian




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