RAID 6 with six 8 TB drives: double-parity safety for high-capacity arrays

How this is calculated

RAID 6 costs two drives' worth of capacity to parity instead of RAID 5's one, but on a 6-drive array that's 33% overhead vs 17%, a reasonable premium for double protection. The write penalty is higher than RAID 5 because the controller must compute and write two parity blocks per stripe, which makes RAID 6 about 10-20% slower on writes than an equivalent RAID 5 array. Read performance is excellent, scaling with the number of data drives (4 in this config). For archival storage, media servers, and backup targets, RAID 6 with large drives is the gold standard.

Verdict

The arithmetic on this config is 32 TB usable from 48 TB raw, sacrificing two drives' capacity to double parity, which carries 33% overhead against 17% for RAID 5 on the same bay count. The trade is worth it because the 8 TB drive rebuild window pushes past 24 hours, which is exactly the range where a second-drive failure during rebuild goes from theoretical to statistically meaningful. Read speed scales with the four data drives (~4x single-drive), and writes cost 10-20% versus equivalent RAID 5 because the controller recomputes and writes two parity blocks per stripe instead of one. For archival storage, media servers, and backup targets the write penalty is invisible in real workloads, and the double-failure tolerance is what makes RAID 6 the gold standard for high-capacity arrays.