Success story and a question about ZFS storage space

[Lyndon Drake]

First off, I want to say a huge thank you to everyone who has contributed to FreeNAS. I had a drive fail, and replacing it went completely smoothly. No data loss — the whole process was entirely straightforward. Thank you all!

I also have a question, which I'm sure is straightforward but for which I cannot find the answer. I apologise if this is because I've failed to understand, but I have read through the documentation and can't figure it all out.

I can't figure out why my free space is so much less than I would expect, based on how much space is used, on my Z2 pool (made up of four 2T disks):

[root@tirith] ~# zpool list remote
NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
remote 7.25T 5.99T 1.26T - 6% 82% 1.00x ONLINE /mnt
[root@tirith] ~# zfs list remote
NAME USED AVAIL REFER MOUNTPOINT
remote 2.90T 515G 512K /mnt/remote
[root@tirith] ~#

The 2.9T used is about what I'd expect from what I can see stored on the drive. So I can't figure out why the ALLOC column in zpool list is so much greater. Any thoughts

 

[mav@]

For RAIDZ2 `zpool list` reports raw disk space usage. Since 4-disk RAIDZ2 pool has about 50% checksum overhead, that is normal to see 5.99T ALLOC there with 2.9T of data written.

 

[depasseg]

bidule0hm has a great zfs calculator.

And don't fall for the marketing hype of a TB. It's actually a TiB which is ~10% smaller than a TB.
https://en.wikipedia.org/wiki/Tebibyte