How To Separate 4 Drive Manually

I just bought EX4100 yesterday, I moved from Dlink DL320L because it only have 2 bay and I need more space right now. I have a question regarding the drive. I used to separate my drive to each hard drive for example Vol_1 to HDD #1 and Vol_2 to HDD #2. This way is easier for me because If my HDD #1 broken then I just back up the data from Vol_1 to another drive and change with the new one and copy back.
Well the problem with EX4100 is it only give JBOD option which when I google, it said that the data is dilute to all drive. So when I lost for example folder ABC, I don’t know where this folder at.
If I use raid 1, I will lost 1/2 of my capacity, If I use raid 5, I will lost 1/4 of my capacity, raid 0, no redundancy at all.
Any chance the NAS can separate the drive manually?
Thanks in advance

That does not sound like JBOD. That sounds like Span or RAID 0.

JBOD should separate all volumes and treat them independently.