Solved Disk space (available + used) != size?

[WayneSilver]

Hello,

Can someone explain this magic to me? I searched the whole web about this problem. All I found out was a tunefs() thing, which reserves 5% to root only data, but even this would not make sense in my case. But how can 75GB of disk space disappear?

root@flserv:/$ df -H
Filesystem  Size  Used  Avail Capacity  Mounted on
/dev/ada0a  5.2G  498M  4.3G  10%  /
devfs  1.0k  1.0k  0B  100%  /dev
/dev/ada0d  2.1G  22M  1.9G  1%  /var
/dev/ada0e  1.0G  8.4M  948M  1%  /tmp
/dev/ada0f  21G  1.6G  18G  8%  /usr
/dev/ada0g  936G  8.2k  861G  0%  /flserv  <---------- Here is my issue

I hope someone can help me with this issue. This is not a partition with some root data on it, it's just a flserv partition for some pictures, music and stuff.

Best regards
WS.

 

[SirDice]

What makes you think you're missing 75 GB?

 

[WayneSilver]

Looking at /dev/ada0g:
Size = 936G
Avail = 861G

Should have mentioned it in my main post sorry.

 

[usdmatt]

https://www.freebsd.org/doc/en_US.ISO8859-1/books/faq/book.html

A portion of each UFS partition (8%, by default) is reserved for use by the operating system and the root user. df(1) does not count that space when calculating the Capacity column, so it can exceed 100%. Notice that the Blocks column is always greater than the sum of the Used and Avail columns, usually by a factor of 8%.

For more details, look up -m in tunefs(8).

936 * 0.92 = 861

 

[WayneSilver]

Okay, makes sense now. Thank you for the fast response.
Should I disable this option? 75GB is quite a[] lot and like I said, there is no system or root data on this partition.

 

[usdmatt]

That I'm not sure of. If you follow through the link in the quote to the tunefs man page, it warns against reducing the reservation, and that settings of <= 5% will force the file system to go into "space optimising" mode which affects write performance.

Having said that, I don't know how old that text in the man page is. It seems unlikely that FreeBSD really needs 5% or more of disks that are 1 TB+ in size. Does anyone else know if this "5% or less greatly increases overhead for writes" warning still stands on disks where 5% is ~50 GB or more?

 

[WayneSilver]

It seems unlikely that FreeBSD really needs 5% or more of disks that are 1 TB+ in size.

Well, I can understand this kind of protection for some system partition. But I don't know why this is also used on normal partitions. I upgraded today on FreeBSD 10 and I don't remember having such things going on on FreeBSD 7.x or 8.x . <- Wrong. Look @ EDIT...
I'm also not the power user, I liked the concept of this OS and used it only for some file sharing at my home . The great thing is: you set it up once properly and then you have 0 problems.

But maybe some other users have any idea about this thing.


EDIT:

Checked some of my old HDD. Same thing there, just didn't realize.