RAID 5 vs. RAID 6 drive space
With RAID 5, you lose the space of 1 drive (for parity). In RAID 6, you lose the space of two drives. For example, using RAID 5 in an array with (16) 1TB drives, your total available RAW space would be 15TB. Using RAID 6, your total available RAW space would be 14TB.
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