Usable disk space - 8 x 2TB RAID-Z2

[chuteless]

I apologize if this has been asked before - I did a search but can't find a definite answer.

I'm fairly new to FreeNAS - I've got a 8 x 2TB drive setup in Raid-Z2. Assuming each disk will lose some space for formatting (I've read each disk should have about 1.82TB usable space), I thought this should give around 10.9TB, but it's showing in FreeNAS and Windows as 10.1 TB.

Are there possible reasons for the 800GB difference, or have I (most likely) done something wrong? All the drives are exactly the same (Samsung F4).

Thanks!

 

[louisk]

If I am doing the math correctly, you should have 6x 2T for data, and 2x 2T for parity for your RAIDZ2 vdev. RAW, you should end up with 12T. Formatted, you will probably end up with 1.8x6 -> 10.8T. So, looks like you're math is correct. The only thing I think of that you mention is that there is going to be a chunk taken out of every disk for swap space, so will eat up a minimum of 16G.

I expect the difference is between exact numbers and rounding to make it easier to read. You can see differences if you do things like 'df -k vs. df -h'.

I don't think you've done anything wrong.

 

[chuteless]

Thanks for the reply - I've looked at the disk space using those commands and it does just look like different numbers being reported.