Centos 5 SAS controller

Have you tried mounting one of the hard disks in a different machine (or setup the RAID card to run it as a JBOD and try the liveCD again), and recover your data that way?

Given that an alien RAID card can make sense of the existing RAID1 array, I'd say your chances are very high.

I'm having the same issue today.
My setup: PowerEdge T100 with Windows Vista Business, SAS 6 IR Raid-1.

2 - WD Black drives 1.5TB not Dell certified, one went bad, replacement from WD is 2TB, not Dell Certified.

I plugged new drive in, it shows up as physically connected, and I can toggle it as a Hot Spare. But there is no way to add it or tag it as a RAID drive in the array.

Solution: Backup the data (& verify backup), delete the existing Array, create a new Array with the 2 dissimilar sized drives, and restore from the backup.

The SAS 6/IR doesn't have the feature set of the PERC & CERC cards - see here, and here.

Good Luck!