HA cluster: installation on 2 indentical servers ?

[alambiki]

Hi Guys,

We are thinking of installing a HA (High availability) for our own needs.
What is the best practice about HA ?
Do we have to configure HA on 2 twin servers ?
Or can the servers be different ?
Is it a matter of Hard Drive ? And can they be Raid 1 Hard drive ?
Thank you for your replys

Pascal