Zpool size less than dataset

[Christopher Klingsäter]

Hi,

I've created a volume through the ZFS Volume Manager (zpool1) with 8 disks of WD Red 4TB in a raidz2 configuration, and then created a zfs dataset on it.

Why is the size of the volume zpool1 equivalent to the available, free space of the disks, and not 20,3 TiB as that's the maximum of the set? How can the windows-dataset be bigger than the volume it's on?

Here's an image to illustrate.

Secondly, why is the maximum size of the 6 disks (taking away two of the eight for parity, raidz2 as stated above) 20,2TB when I map the CIFS share to Windows, and not 22,3TB as that's what I thought it should be?

I'm aware that the 4TB is pure marketing, but losing 3,8TB on 6disks seems a bit too much?

I would really appreciate someone explaining this to me like I'm a 6-year old :)

 

[cyberjock]

Yes, we know all of this.. and there's plenty of threads on this topic as well as bug tickets. It's all about understanding where data is coming and going. ;)

 

[enemy85]

Conversion TB->TiB? :)

 

[Christopher Klingsäter]

Conversion TB->TiB? :)

Sure, 20,3 TiB equals 22,3TB, I'm with you on that. But, why then does Windows only show a size of 20,2TB?

 

[Christopher Klingsäter]

Yes, we know all of this.. and there's plenty of threads on this topic as well as bug tickets. It's all about understanding where data is coming and going. ;)

Well then, let me ask you, don't you think I searched for it before posting? Perhaps I'm using the wrong terminology than what other people wrote about to describe the problem. ;)

Either way, can you provide some links where I (and others) can find the solution? Is it a bug in the GUI or a feature? All I've been able to find is stuff about quotas, which I haven't used here since that's about using less than the total available space.

I've never understood the Unix and Linux community when it comes to forums and the reluctance to answer questions more than once. If duplicates are so bad, make a sticky about everything and see how well that works out.

 

[enemy85]

With hd in freenas u "lose" space twice:
First considering that 1TB hd are less that 1tb because considered as 1.000.000.000.000 , secondly because of TiB

 

[enemy85]

1TB=931Gb
931*4*6*0,9095 minus swap space that is 2gb each disk

 

[Christopher Klingsäter]

Thank you! I just found out that Windows actually displays TiB in Explorer, and not TB like it says. Confusing...

On to my first question then, how come the dataset size is greater than the size of the volume? I've obviously not understood something fundamental, it seems :)