Dec 282010
 

Here I go, removing an old ZFS dataset that is no longer required. But first, some stats (which have been edited to remove non-zfs output):

[dan@kraken:~] $ df -h
Filesystem                    Size    Used   Avail Capacity  Mounted on
storage                       1.4T     15G    1.4T     1%    /storage
storage/bacula.DO.NOT.USE     5.8T    4.4T    1.4T    76%    /storage/bacula.DO.NOT.USE
storage/compressed            1.4T     49K    1.4T     0%    /storage/compressed
storage/compressed/bacula     4.4T    3.0T    1.4T    68%    /storage/compressed/bacula
storage/compressed/home       1.4T    2.7G    1.4T     0%    /storage/compressed/home
storage/pgsql                 1.4T    5.5G    1.4T     0%    /storage/pgsql

And the list:

$ zfs list
NAME                        USED  AVAIL  REFER  MOUNTPOINT
storage                    7.47T  1.41T  14.5G  /storage
storage/bacula.DO.NOT.USE  4.38T  1.41T  4.38T  /storage/bacula.DO.NOT.USE
storage/compressed         3.07T  1.41T  49.1K  /storage/compressed
storage/compressed/bacula  3.07T  1.41T  2.96T  /storage/compressed/bacula
storage/compressed/home    2.75G  1.41T  2.75G  /storage/compressed/home
storage/pgsql              5.50G  1.41T  5.50G  /storage/pgsql

Now we destroy:

[dan@kraken:~] $ sudo zfs destroy storage/bacula.DO.NOT.USE
Password:

And afterwards:

[dan@kraken:~] $ df -h
Filesystem                    Size    Used   Avail Capacity  Mounted on
storage                       5.8T     15G    5.8T     0%    /storage
storage/compressed            5.8T     50K    5.8T     0%    /storage/compressed
storage/compressed/bacula     8.7T    3.0T    5.8T    34%    /storage/compressed/bacula
storage/compressed/home       5.8T    2.7G    5.8T     0%    /storage/compressed/home
storage/pgsql                 5.8T    5.5G    5.8T     0%    /storage/pgsql

And…

[dan@kraken:~] $ zfs list
NAME                        USED  AVAIL  REFER  MOUNTPOINT
storage                    3.09T  5.79T  14.5G  /storage
storage/compressed         3.07T  5.79T  49.1K  /storage/compressed
storage/compressed/bacula  3.07T  5.79T  2.96T  /storage/compressed/bacula
storage/compressed/home    2.75G  5.79T  2.75G  /storage/compressed/home
storage/pgsql              5.50G  5.79T  5.50G  /storage/pgsql

What I do not understand is why storage was 1.4T available, and is now 5.8T available. The dataset I destroyed was 4.4T used, plug 1.4TB available, gives the 5.8T. Now I see. I was comparing USED with AVAIL and not getting the math right.

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