ZFS RaidZ1 parity overhead

based on: calc @ https://wintelguy.com/zfs-calc.pl
Parity Overhead with 4000GB drives (RaidZ-1, 512b sectors)
---------------------------
numdisks = TB overhead

 2= 3.985730 (Mirror)
 3= 3.985730 (RaidZ-1)
 4= 4.009038    "
 5= 3.985730    "
 6= 4.037492
 7= 4.071858
 8= 4.121299
 9= 3.970459  <-- smaller overhead than 2 or 3 disks!
10= 4.180835
11= 4.054936
12= 4.099608
13= 4.111303
14= 4.023575
15= 4.342274
16= 4.189380
17= 3.977645  <-- smaller overhead than 2 or 3 disks!
18= 4.204015
19= 4.462724 (high)
20= 4.133349
21= 4.332890
22= 4.560937 (high)
23= 4.110861
24= 4.283172
25= 4.455484
26= 4.652411 (high)
27= 4.050832
28= 4.174837
29= 4.340177
30= 4.505518 (high)
31= 4.629523 (high)
32= 4.794863 (highest)
33= 3.998224 <-- almost as small overhead as 2 or 3 disks!