Anomalous disk usage in pfSense 2.5.1

roldor

Hi, everyone

I have found out an anomalous disk usage in my pfSense instance. Here you are console output:

[2.5.1-RELEASE][root@morannon.ednonlabs.com]/: df -h
Filesystem                     Size    Used   Avail Capacity  Mounted on
/dev/ufsid/591e12427abe4feb     48G    1.5G     43G     3%    /
devfs                          1.0K    1.0K      0B   100%    /dev
/dev/md0                       3.4M    128K    3.0M     4%    /var/run
devfs                          1.0K    1.0K      0B   100%    /var/dhcpd/dev

As you can see total size (48G) does not correspond to the sum of available space (43G) and used space(1.5G).

What could be the reason of this behaviour?

Thanks in advance

Gertjan

@roldor said in Anomalous disk usage in pfSense 2.5.1:

What could be the reason of this behaviour?

What about :
48G minus 1.5G = 46,5 G.
Available is 43G. You miss 46.5 - 43 = 3.5G.
1.5G is the space used by files - folders and files you can delete, etc.

The missing 3.5G could be :
Partition alignment.
The two FAT - or the 'inode' table(s)
The root directory.
Other internal file structures, whatever FreeBSD for this type of file system.

Btw :

[2.5.2-RELEASE][root@pfsense.my-domain.net]/root: df -h
Filesystem                     Size    Used   Avail Capacity  Mounted on
/dev/ufsid/54ca20c41b3d50b0    285G    7.0G    255G     3%
.....

which means (285-255)-7= 23 Gb 'gone' :)
But, I don't care. It's a router, not a NAS.

You shouldn't test the ZFS file system, I've heard it far worse ;)

Also : the same story is probably valid for fat32, NTFS, etc.

roldor

Hi, @gertjan

Thanks for your answer. Nervertheless, I would like to know the main reason of this behaviour.

Regards

Gertjan

@roldor

Ok, you asked for it.

Start reading here.

Btw : as you might know, as disk type device is known as a "block device".
When you store a file with one byte in it, or 200 bytes, at least 1 block will get allocated. This is often a sector, or a set of sectors on the physical device.
So, at least, 512 are 'gone' even when you use 1 or 20 bytes.

For each file, 256 bytes are lost.

I advise you to locate a nice Youtube video that explains what a file system is, or UFS (used by pfSense == FreeBSD) or ZFS, if you use that.
See https://docs.freebsd.org/en/books/handbook/filesystems/

stephenw10

See: https://docs.freebsd.org/en/books/faq/#disk-more-than-full

(43G+1.5G)x108% = ~48G

Steve

roldor

Hi, @Gertjan and @stephenw10

Thank you for your answers.

Regards