ZFS and df weirdness

[Christian Walther]

Hi Dan,

basically the "size" in df shows the current free space plus the used
space of the specific filesystem. This makes sense: Since per default
all disk space is shared, and thus can be used by all filesystems, all
filesystems need to report it as free space. Well, and used space has
to be added to the complete size, of course.

In your setup, there are 1.5TB available, but DATA uses 292GB (rounded
to 300GB). Both value add up to 1.8TB, giving the overall size of your
pool. (There is another rounding error because of your other
filesystems, but they are rather small.)
If you, say, add 400GB to tank/home/jago your df would look something like this:

> tank/DATA          1.4T    292G    1.1T    16%    /DATA
> tank/home/jago     1.1T    400G    1.1T     0%    /home/jago

It needs some time to get used to the way df displays data. IMO things
are getting easier when one remembers that the OS actually treats
every Z Filesystem like an individual device.
And BTW: The real fun starts when you add reservation and quotas to
some of your filesystems. ;-)

HTH
Christian