Why so many different Max Storage Figures

[Thousandbuckle]

Hello all, I just put together a new FreeNAS Box (9.10 Sttable) with 8 x 4TB WD Red drives. I chose the configuration below for a RaidZ2 which estimates volume capacity at 21.82TB. I then created a new Volume which shows 2 different Max Storage capacities. One is 29TB and the other is 20TB, neither one is what the Volume Manager Wizard showed.

Can some one explain how this is working and what my Max Storage Capacity really is?

 

[Bidule0hm]

20 TiB ;)

Please read this and this :)

 

[Robert Trevellyan]

One is 29TB and the other is 20TB

What he said, and the first is raw space (8 x 4TB), while the 2nd is pool space after redundancy and overhead is estimated (< 6 x 4TB).

 

[Thousandbuckle]

Thank you for the links, that helps me understand that aspect of storage better now.