You can choose beteeen maximum Space and maximum availability.
Each Node have 7.4TB gross.
2x 7.4TB with Network Raid 0 = 14TB
If one complete Node fails, you have nothing.
2x 7.4TB with Network Raid 1 = 7TB
If one complete Node fails, you have remaining 7TB online.
You can create Volumes with R0 and R1 at the same Time.