VNX5200 Disk Failure & Unbound Disks

Hi Guys,

I have a disk failure in my VNX5200:

Bus 1 Enclosure 0 Disk 10 taken offline. Replace the drive. SN:KWJ96T7R

The Array has successfully added an unbound disk to the RAID to cover the failure:

Copy of all LUNs/all RAID groups from disk 1_0_10 to disk 1_0_11 finished

This is good. But now i have the error that my Hot spare policy is no good and it wants another disk. I have around 5 unbound disks across 2 enclosures (only 1 unbound in Bus1, 4 unbound in Bus 0) 

My question is this. 

If the VNX loses another disk will it automatically use one of the unbound disks I have across the enclosures? or do i need to replace the failed disk?

If the VNX does use an unbound disk how do i get the Hot Spare Policy to recognise there is more that 1 disk available (unbound)? 

If someone could point me in the right direction with this that would be really appreciated. 

Many thanks.