FBWC and Zero Memory (ZM) RAID Controller on HP DL360p

I got a chance to work on HP DL360p Gen8 server with Smart Array controller P420i/ZM

1. What are the advantage of having FBWC or BBWC
2. Will it be possible to add an external P420/1GB or P420/2GB to this server.
3. Can a FBWC give better performance for RAID rebuild for replacement hard disk (we use RAID 1)
4. Overall performance could get affected by Zero Memory controller ?

Can someone please share your insight on this.

FBWC is the only option for modern HP controllers. BBWC is not offered anymore.

There is very little practical use for the Zero-memory controller unless local disk performance isn't important to you.

Otherwise, you will always want to have a cache available... this is necessary for some of the RAID controller options and being able to use SSDs.