activate raid with data on system with 2 hdd 1 tb each

i have a trouble just like at the subject, i have ubuntu server 64 bit rel. 9.1
my rayd controller is a promise fasttrack 2400, with two port sata 2 and working on raid 1 with 2 hdd wd 1tb 7200 rpm.
Linux os is mounted on other hdd sata2 with wd 250 gb capacity.
how can i use the raid ? and also i'd like don't detroy data on that array hw if is possible,someone can halp me?
thank a lot
Marco Canali