I have a pool of 28 2TB-disks (56T) in 4 arrays of 7 disks. Since it's raidz1 (~RAID5), I'd expect 1 disk to be used for parity in each array, so the resulting volume should be 2TB*4*(7-1)=48TB, right?
Now, what I see on my system:
$ zpool list volume NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT volume 50.5T 308K 50.5T 0% 1.00x ONLINE - $ zfs list volume NAME USED AVAIL REFER MOUNTPOINT volume 2.00T 40.3T 75.8K /volume $ df -h /volume Filesystem Size Used Available Capacity Mounted on volume 42T 75K 40T 1% /volume
So, there are only 42T instead of 48T. Where are the missing 6TB? And where does the number 50.5T come from?