Volume too small?

[morxy49]

Just completed my new build, and now i created the volume.
The volume is 8x3TB drives in RAIDz2, and the size of the volume is 15.2 TiB.
Isn't 15.2 TiB too small.
When i calulated it i got it to 16.32 TiB.
(8*2.72)-(2*2.72) = 16.32TiB

 

[morxy49]

ok, so i redid the volume, and dragged around the little box-thingy, and managed to get 16.36TiB, but... when i create the volume, it shrinks to 15.2TiB. what!? what's going on here? :(

 

[cyberjock]

Yeah...

Check out https://bugs.freenas.org/issues/4419

Already known and already documented. ;)

Do "zfs list" and you'll see actual available/used disk space. The sum of used and avail(assuming no snapshots, datasets with reserved, etc. are used) should be your total pool size.

 

[morxy49]

Yeah...

Check out https://bugs.freenas.org/issues/4419

Already known and already documented. ;)

Do "zfs list" and you'll see actual available/used disk space. The sum of used and avail(assuming no snapshots, datasets with reserved, etc. are used) should be your total pool size.

but... what about this then?
when i add the NAS as a network drive in windows it also says 15.2TB (it means TiB of course, but it's windows...)

EDIT: but as long as the real size actually is 16.36TiB, it doesn't matter. that is what you're saying, right? ;)
just want to make sure :P

 

[memario]

Due to the fact that you have created a non optimal pool/vdev, some space is lost in ZFS due to padding. The amount of space lost varies based on how you compose your pool/vdev. This link should give you some idea of the padding and zfs overhead between different vdev setups and also explains why padding in ZFS occurs.

The ZFS volume manager shows the amount of raw free space, it does not take into account things like ZFS overhead and padding.

After the volume is created the available space shown is based on the 'zfs list' command. This command corrects for things like ZFS overhead, padding and compression (in the future).