RAID 5 BCVs are not supported for the protect_data option. You can protect data byusing a mirrored BCV device  you must specify thename of a bcv_meta that matches the original metadevice in capacity, stripecount, and stripe size.
I've tried this a couple of times in the SMC gui. I have a 50GB striped metavolume that I want to expand and protect the data at the same time. I created a 50GB BCV striped metavolume. In SMC, I highlight my prod device, select FBA Meta Device Config - Add/Remove Meta Members, check the radio button to Protect Data and when I choose to select the BCV Meta Head, there's nothing there. It doesn't see the BCV Metavolume I created.  What step am I missing?  Thanks.  Jim
vmax metadevice expansion and protecting data