How to correctly calculate space in ZFS?

Question

linux

Guys, teach me how to count space in zfs :) The
question seems absurd, but look.
Created raidz-2 from 10 HDDs of 500GB each.
Purely logically, it turns out that two disks are a hash, which means that there should be 4TB of free space (+ -).

BUT!
In spool list - I get 4.5TB free
In zfs list - 3.34TB

How is it at all?

Answer 1

zpool shows free space without deducting control blocks (they are not there yet).
zfs shows (roughly) what you need.
if there were no overhead, then you would see 3.6T:

((500 ⋅ (10^9)) ⋅ (10 − 2)) / (1024^4) ≈ 3.637978807091713