Struggling to understand zfs dRAID (calculator)
I'm adding 12x8TB drives to my server. I'm looking at two dRAID configs - one with a bigger safety net than the other. But I'm not understanding the configs. The configs would be:
Config 1:
draid1:10d:12c:1s
I'd expect this to have 10x8TB(ish) space - 80TB usable, 8TB for parity and 8TB for Spare.
Config 2:
draid2:8d:12c:2s
I'd expect this to have 8x8TB(ish) space - 64TB usable, 16TB for parity and 16TB for Spare.
But that's not what the graph shows at all - Config1 shows ~70TiB usable with 8 Data Disks and capacity drops to ~55TiB if I have 10 data disks. This doesn't make sense to me since 8x8TB disks would never fit 70TiB's worth of data...
Config 2 looks more like I'd expect it - around ~55TiB with 8 data disks since I'm using about 4 disks' worth for redundancy.
What am I doing wrong?