[CentOS] server mirroring how to

[Kwan Lowe]

2009/8/1 fabian <fabian at baladia.gov.kw>:
> 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

[snip]

> 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

Setting up DRBD and a heartbeat for a service is not at all difficult.
 Take a look at HowtoForge for a simple example using Apache.

DRBD does mirror a block device on two servers. It takes two local
filesystems and creates a virtual filesystem that you can then
subdivide with LVM.  Writes to the virtual filesystem is then mirrored
to both.

The heartbeat service does a few things, but in a nutshell it can move
a virtual IP address between two machines. Users will use the virtual
address as the web server.

There are more complex ways if you want to load-balance the servers.

DNS is also pretty simple. You can either load the same zone files on
both and then use one as a primary and one as a secondary. No
heartbeart or anything special is required. There are better methods
with replication that are slightly more involved to configure, but
shouldn't take more than a few hours.

Squirrelmail is also not too bad to configure. If you have the home
directories on DRBD it works transparently.

The mail setup is the only thing that I've not done.