[CentOS] smartest way to setup new system (DELL PE 4600)

Hi all,

One of our servers (very old) died last week and I'm setting up a new 
CentOS 5.1 box to replace it.  Primarily used as a samba fileshare on a 
mostly windows-workstation network.

This system will, ideally, have the OS on a 146 GB SCSI drive, with user 
data on a 300GB SCSI, both attached to the backplane of the 4600.

My question is this:

What's best practice and most desirable partitioning for doing this, and 
how would I go about setting up mirrors of both the OS and the user data 
drives?

Thanks in advance for any help on what I know is a rather newbie 
question....please chalk it up to lack of sleep and veritable hounding 
by the 'higher ups' :)

Kind regards,
-Ray