ZFS Pool showing incorrect size

Phobios

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Since receiving a couple of disks I have now created what should become my final file server, and with that I have created a ZFS pool by running zpool create server raidz2 /dev/da{0..3}.eli /dev/ada{0..7}.eli and the pool is created, but when I check df -h on /server, it only shows it as 80TB. Each disk is 10TB, whereas diskinfo shows it as 9.1TB. With 12 disks in a raidz2 configuration I should at least have 91TB of free space instead of 80? Am I correct or am I missing something? zpool status shows no errors. If there is an error here, how do I debug it?

Tried creating raidz and raidz3 with the disks and those gave me 94T and 77T respectively.
 

Bobi B.

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Would you mind posting commands you run and their output? Besides most advices are against running df(1) against ZFS.
 
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Phobios

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Bobi B. What is recommended to use for checking against ZFS? zfs list shows the same value. I followed the commands to create my encrypted pool from this blogpost: https://www.daveeddy.com/2015/12/04/zfs-zpool-encryption-with-geli-on-freebsd/, and none of the commands showed anything out of the ordinary.

SirDice Yes, I am aware, but it still doesn't add up. A bit of reading tells me there is insane overhead used by raidz2 though. Could it be because I use an awkward amount of disks? I recall reading a year back or so that it could be more efficient, space-wise, to use a power-of-two number of disks.
 

SirDice

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I recall reading a year back or so that it could be more efficient, space-wise, to use a power-of-two number of disks.
With a bigger number of disks the size difference would get smaller, yes. It's going to matter if you use 4 disks (with 2 for fault-tolerance; 2 effectively usable) or 10 disks (2 fault-tolerance; 8 usable). It doesn't necessarily have to be a power of two, it's perfectly fine to have 5 or 7 disks for example. If I recall correctly the "magic" number of ideal disks in a vdev is 6 (which isn't a power of two). But this has more to do with performance than size.
 
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