problem with netraid

[ennio]

i have an lxrpro server with a netraid controller (d4943a).
i have an external disk system with two disks of 36 gB configured in raid1.
One disk fail , so i chenge it, but when i start the rebuil process, it hangs after 10 minutes, so i see a message that tell me that the first disk has a media error.
I also try to repeat the rebuild process, but the result is always the same.

How can i rebuil my raid ?

thanks.