Thinking on migrate from freeNAS to Rockstor

I guys,

I have one FreeNAS HP Gen 8 box with 4 x Tb HDs and 12Gb ECC and I’m not so happy with corral update, It becames vey sludge.

One thing I’m afraid of leaving FreeNAS is ZFS. I want in this post know from you if BTRFS nowadays is comparable to ZFS. What happen if I loop an Disk? The system send’s me an e-mail or something?
Can I have some foldes with extra protection (multiple versions, more copies)

What I realy want here is about your cases of disk failure and how rockstor behaved and recomendations how can I configure my Raids.