Questions about adding disks to running system

I have a VNXe3200 with 11 - 600GB 10K disks and 2 - 200GB Flash drives set up as Flash Cache

The 10 of the 600GB drives are in a Performance pool RAID5 4+1 with 1 drive as a hot spare.  The Flash drives are mirrored with no hot spare.

I've ordered an additional 5 - 600GB drives and 1 - 200GB flash drive.  I've read the installation guide but I just wanted to make sure I understand the process.  I will be installing the drives one at a time with at least a 10 second gap between each one, as outlined in the guide.  I will then go to Unisphere and add the drives to the existing Performance Pool as RAID5 4+1.

So my questions are, what happens to the data already in the performance pool?  Will existing pools remain on the original 10 drive configuration or will they have access to all 15 drives once the system is configured and balance themselves out?  Additionally, will the Flash drive be recognized as a hot spare or is there something that I need to do for that?  Finally, are there any issues doing this while the array in in production and serving up NFS datastores to VMWare?

Thanks for any help.