[CentOS] What's The Odds?

What's the odds of retaining the data in a software raid-1 array when 
falling back to CentOS 5.8 x86_64 from CentOS 6.3 x86_64? The array is 
made up of 2 - 1.5 TB hard disks.  The original array was defined under 
CentOS 5.3 x86_64, then CentOS 6.1 x86_64 was installed and over time 
upgraded to CentOS 6.3. I need to back-level to test some software not 
certified for CentOS/RHEL 6.
 
Thanks,
Gene Poole