Available space 8 bay with 3 drive sizes

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Sandshark wrote:

RAID6 needs at l;east three drives, 

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Actually in the ReadyNAS it requires at least 4 drives.   Triple RAID-1 would be a simpler option for dual redundancy with three drives - but the NAS wouldn't do that either.

Note that if you use the usual equations for P and Q here: https://igoro.com/archive/how-raid-6-dual-parity-calculation-works/ then RAID-6 with three drives has the same on-disk layout as triple RAID-1 (P and Q would both be equal to the original data block).   So there's no reason to waste time with parity math or rotating data and parity blocks - you might as well just do triple mirroring.

powellandy1  wrote:

So why is all space not being used here (3x10tb, 4x8tb, 1x6tb)??

Each layer has at least 3 drives.

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Because the NAS won't do RAID-6 with three drives.

Also, you'd need to install the drives in order of size.  Assuming that was done, XRAID would have 8x6TB and 5x2TB RAID groups. Then there would be 2 TB on each of the 10 TB drives that couldn't be used.

However, the breakdown in the RAID calculator incorrectly states the volume size.

8x6TB -> 36 TB of capacity + 12 TB of redundancy

5x2TB -> 6TB of capacity and 4 TB of redundancy

3x2TB -> 6 TB of unused disk space.

Total capacity is 42 TB (~38.2 TiB) - not 41.7 TiB as stated in the calculator.

Total redundancy is 16 TB  (~14.6 TiB)

Total unused is 6 TB (~5.46 TiB)