SOLVED displayed space vs "zpool list main"

[umproko5]

I have the following,
# zpool list main
NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
main 1.73T 715G 1.04T - 19% 40% 1.00x ONLINE /mnt

And from the GUI see attached.
669.7+476.2=1145.9

Where is the 600GB?

Thanks.

 

[Bidule0hm]

It's taken by the parity, the checksums, the blocks overhead, ...

 

[umproko5]

so just wondering .... with 6 4tb drives running raid z2 what would be the estimated usable space? Would it be close to 16tb?

 

[Bidule0hm]

First you need to convert TB in TiB --> 4 Tb * 0.909 = 3.64 TiB

Then you have 2 drives for parity and 4 for the data --> 3.64 * 4 = 14.56

Then there is the space taken by the checksums and the blocks overhead, there is no exact number for the latter and I don't know the number for the former, but on my server it's about 12% for both --> 14.56 - (14.56 * 0.12) = 12.81

Finally it's not recommended to use more than 80% of the pool size (for performance reasons; use over 80% and the drop is significant, use over 90% and the drop is abysmal...) --> 12.81 * 0.8 = 10.25

So the final user (recommended) usable space is roughly 10 TiB ;)

 

[umproko5]

thanks for the info.