Mirrored Pool is 300GB less than drive sizd

[VenomBottle]

Hello,

I just finished building my first NAS. I’m using 2x 10TB drives (9.1TB in reality).
I set up a mirror pool with them and the resulting pool size is 8.79TB. So more than 300GB less. Seems a bit excessive for overheads. I haven’t been able to find much on this topic on the internet. Is this typical or did I mess up? If it is normal, can anyone elaborate on what that 300GB is being used for? Thanks!

 

[Samuel Tai]

gpart list will show the partitioning of your pool drives. By default, a 2GiB swap partition is created in front of the ZFS partition, which takes the remaining space. The rest is the typical confusion between decimal GB and base-2 GiB. You can tune the swap partition reservation size under System->Advanced.