Which tool do you use?
You can assign an unused drives as hot spare for 1 or multible logical drives. In your case it should be possible to assign the unassigend drive as hot spare for both logical drives.
As far as I remember, there has been some fw issues in the past, with drives reporting to be slightly smaller than other models with the same size, hence it could not rebuild.
In you case i would replace the failed drive with the unassigned drive.
Even if you get the unused drive assigned as spare, the Smart Array still want you to replaced the failed drive. And it will remain in interim recovery mode untill you replace the failed drive.
When you got a hot spare, it will kick in, when you get a drive failure. And when you replace the filed drive, it will copy the data back to the new drive, and the hot spare will become spare again.
So:
1. Replace the failed drive.
2. Get BIOS / FW and drivers updated.
BR
/jag
