Readynas 3200 disk space issue

Paladax wrote:
Thanks, that explained the why a little better. Only now it is a bit more confusing because if i do that command from the root folder of my backups it tells me my backups are 22TB.. however the NAS itself it only 18TB.

Right. For example, imagine a parent directory containing four empty child directories:

NAS2:~/parent# du -h
4.0K    ./child0
4.0K    ./child3
4.0K    ./child1
4.0K    ./child2
20K     .

Now we create a 100MB file in child0, and create hardlinks to that file in child1, child2, and child3:

NAS2:~/parent# dd if=/dev/zero of=./child0/file count=204000
204000+0 records in
204000+0 records out
104448000 bytes (104 MB) copied, 2.19748 s, 47.5 MB/s

NAS2:~/parent# ln ./child0/file ./child1/link1
NAS2:~/parent# ln ./child0/file ./child2/link2
NAS2:~/parent# ln ./child0/file ./child3/link3

To the "ls" program, each of the links looks like a 100MB file:

NAS2:~/parent# l -Rh
.:
total 16K
drwxr-xr-x 2 root root 4.0K Mar  6 13:06 child0
drwxr-xr-x 2 root root 4.0K Mar  6 13:07 child1
drwxr-xr-x 2 root root 4.0K Mar  6 13:07 child2
drwxr-xr-x 2 root root 4.0K Mar  6 13:07 child3

./child0:
total 100M
-rw-r--r-- 4 root root 100M Mar  6 13:06 file

./child1:
total 100M
-rw-r--r-- 4 root root 100M Mar  6 13:06 link1

./child2:
total 100M
-rw-r--r-- 4 root root 100M Mar  6 13:06 link2

./child3:
total 100M
-rw-r--r-- 4 root root 100M Mar  6 13:06 link3

But if we do a "du", we see the truth:

NAS2:~/parent# du -h
100M    ./child0
4.0K    ./child3
4.0K    ./child1
4.0K    ./child2
100M    .

Unless we use the "-l" option to force du to treat links as though they're files:

NAS2:~/parent# du -hl
100M    ./child0
100M    ./child3
100M    ./child1
100M    ./child2
399M    .

Paladax wrote:
If that is right though it would explain why the other 18TB was filling up when I tried to mirror the data onto it while the source one was still showing only 42% full.

Yes. The program performing the copy was treating links as though they were the linked-to files. If you had used it on my example, it would have created four 100MB files on the destination drive rather than one 100MB file and three links.