If you can make each drive available separately to the OS, then you could easily run software RAID on top of them. With Linux this can be done with mdadm. I'm sure Windows has something similar.
I don't know exactly how your hardware works, but you could split it into two JBODs visible to the OS as two separate drives. Then you could use mdadm to configure that as a simple RAID-1 setup, mirroring the two drives. Then if one of the component drives in one of the jbod failed, you could rebuild it from the other jbod.
However, this all does add an extra layer of complexity to your setup, and lots of potential extra failure modes. I would advise you to think about turning off all disk-spanning via jbod on the device, and just use mdadm (and possibly lvm) to combine the individual drives from your device. Ideally the device does make this possible by exposing all the individual drive devices.
So to recap, keep things simple on the device and expose individual drives to the OS if possible. Then use software raid and logical disks to partition it up and provide redundancy.