SI and binary prefix and ZFS on top got me all confused

[Junicast]

I have 5 drives offering each 4 TB which equals 4,000,000,000,000 Bytes and ~ 3.64 TiB per drive, right?
So if I would use them as JBOD this would result in ~ 18.2 TiB, right?
Actually I happen to use RAIDZ2 which is said to be similar to RAID6. If I were using RAID6 this would result in 3 x 3.64 TiB = 10.92 TiB.
I'm on FreeNAS 11.1 and my WebGUI tells me the following:
used: 13.9 TiB
available: 4.3 TiB
If I'm not all the way stupid this sums up to 18.2 TiB.
How does this fit together? I'm very confused.

 

[danb35]

http://doc.freenas.org/11/storage.html#view-volumes

Note that in this example, there are two datasets named volume1. The first represents the ZFS pool and its Used and Available entries reflect the total size of the pool, including disk parity. The second represents the implicit or root dataset and its Used and Available entries indicate the amount of disk space available for storage.

 

[Junicast]

I would not have thought that it was that easy. Thank you.

 

[Ericloewe]

I'll say this again, for the benefit of future readers:

The FreeNAS manual really is excellent, and it keeps improving. It removes a lot of confusion and guesswork from the equation. It's definitely worth a read, besides being used as a reference.