Missing 2 TB?

[brando56894]

Edit: I should have done the conversion myself before I wrote up this long post. 12 TB = 10.9 TiB which is a pretty large disparity. I remember being pissed off when losing 80 GB out of a 1 TB drive sucked, now I'm losing 1.1 TB!


I purchased 3x4 TB HGST HDDs (but had to return two of them because they were DOA) and I used the working one to replace a 3 TB drive in my pair (3 TB and 4 TB, 2x4 TB, 2x1 TB, 2x3 TB ) and it seems like I'm missing 2 TB worth of space. I have a total of 10 TB of useful space in my pool

Code:

[root@freenas] ~# zpool list Multimedia
NAME         SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
Multimedia  9.97T  8.19T  1.77T     16.0E    21%    82%  1.00x  ONLINE  /mnt

But according to the size of these drives I should theoretically have 12 TB. Am I missing 2 TB because of the decimal to binary conversion or because this mirrored pair was previously 3 TB (one 4 TB drive, one 3 TB drive) so when it resilvered it only used 3 TB?

 

[gpsguy]

Obviously, you've figured out the part of the issue. In addition to that, 20GB 2GB is set aside on each drive for a swap partition. While you probably won't run out of RAM, it's mainly used for disk swaps when the sizes don't match up exactly. FreeNAS also uses some overhead.

It's a common question and unfortunately it's not documented very well. See some of the threads mentioned in this "bug": https://bugs.freenas.org/issues/12968

Edit: I should have done the conversion myself before I wrote up this long post. 12 TB = 10.9 TiB which is a pretty large disparity.

 

[danb35]

20GB is set aside on each drive for a swap partition.

I'm sure you meant 2 GB, not 20 GB.

 

[gpsguy]

Yes, a typo. Thanks for pointing it out.

I thought about tagging you and letting you explain it, yet again. I figured it was easier just to point to the bug you filed.

I'm sure you meant 2 GB, not 20 GB.

 

[danb35]

Probably better too--that way he can see six different ways I've explained it, rather than just one.