software RAID 1 and upgrades

[Jack Howarth]

    Before I proceed with setting up our next Linux box with
dual SATA drives to use a RAID 1 software mirror, I have one
additional question about future upgrades on such a box. If one
uses the software RAID 1 mirror approach, how exactly should 
future upgrades be handled? Does the RedHat installer normally
recognize the pre-existing RAID 1 and 'mirror the upgrade'
as it is done. Or do you have to explicitly cause the mirror
drive to be sync'ed with the newly upgraded system drive
after rebooting?
                           Jack