ext4 works fine, use it, compatible with all raid cards and arrays
most uppity raid cards have a bios to work with too
SERVER: Azure datacenters, Hyper-V
But it seems that my current card doesn't support JBOD so I decided to use RAID6. Then again the NAS4Free server isn't deployed yet, and I think I'll wait for another server which we also ordered. I believe it can support JBOD and I'll swap their RAID controllers.