Where did disk space go in zfs?

Question

FreeBSD

The size of the volume is 14.5T and the size of the data set created on this volume is 6.09T.
No quotas have been set.

# zpool get size                                                                                                    
NAME          PROPERTY  VALUE  SOURCE                                                                                               
hdd1          size      14.5T  - 

# zpool get all hdd1                                                                                                
NAME  PROPERTY                       VALUE                          SOURCE                                                          
hdd1  size                           14.5T                          -                                                               
hdd1  capacity                       22%                            -                                                               
hdd1  altroot                        /mnt                           local                                                           
hdd1  health                         ONLINE                         -                                                               
hdd1  guid                           3863011763114068054            default                                                         
hdd1  version                        -                              default                                                         
hdd1  bootfs                         -                              default                                                         
hdd1  delegation                     on                             default                                                         
hdd1  autoreplace                    off                            default                                                         
hdd1  cachefile                      /data/zfs/zpool.cache          local                                                           
hdd1  failmode                       continue                       local                                                           
hdd1  listsnapshots                  off                            default                                                         
hdd1  autoexpand                     on                             local                                                           
hdd1  dedupditto                     0                              default                                                         
hdd1  dedupratio                     1.00x                          -                                                               
hdd1  free                           11.3T                          -                                                               
hdd1  allocated                      3.20T                          -                                                               
hdd1  readonly                       off                            -                                                               
hdd1  comment                        -                              default                                                         
hdd1  expandsize                     -                              -                                                               
hdd1  freeing                        0                              default                                                         
hdd1  fragmentation                  20%                            -                                                               
hdd1  leaked                         0                              default                                                         
hdd1  [email protected]_destroy          enabled                        local                                                           
hdd1  [email protected]_bpobj            active                         local                                                           
hdd1  [email protected]_compress           active                         local                                                           
hdd1  [email protected]_vdev_crash_dump  enabled                        local                                                           
hdd1  [email protected]_histogram     active                         local                                                           
hdd1  [email protected]_txg            active                         local                                                           
hdd1  [email protected]_birth             active                         local                                                           
hdd1  [email protected]_dataset     enabled                        local                                                           
hdd1  [email protected]_data          active                         local                                                           
hdd1  [email protected]              enabled                        local                                                           
hdd1  [email protected]_limits      enabled                        local                                                           
hdd1  [email protected]_blocks           enabled                        local


# zfs get quota hdd1                                                                                                
NAME  PROPERTY  VALUE  SOURCE                                                                                                       
hdd1  quota     none   local 

# zfs  list                                                                                                         
NAME
hdd1                                                   6.09T   728G   140K  /mnt/hdd1                                               
hdd1/.system                                           64.7M   728G   151K  legacy                                                  
hdd1/.system/configs-5ece5c906a8f4df886779fae5cade8a5  44.8M   728G  44.8M  legacy                                                  
hdd1/.system/cores                                     17.8M   728G  17.8M  legacy                                                  
hdd1/.system/rrd-5ece5c906a8f4df886779fae5cade8a5       140K   728G   140K  legacy                                                  
hdd1/.system/samba4                                     523K   728G   523K  legacy                                                  
hdd1/.system/syslog-5ece5c906a8f4df886779fae5cade8a5   1.36M   728G  1.36M  legacy                                                  
hdd1/ESXi                                              4.06T  4.39T   389G  -                                                       
hdd1/ESXi1                                             1.02T  1.57T   158G  -                                                       
hdd1/backup                                            1.01T   728G  1.01T  /mnt/hdd1/backup

Answer 1

Tried
zfs list -t snapshot ?

Answer 2

copy-on-write filesystems like ZFS don't free up space on deletion,
and even more so if you've used zfs clone or zfs snapshot.

Answer 3

They will prompt here: forum.ixbt.com/topic.cgi?id=109:256

Answer 4

It's not clear what's bothering you. You have reserved your space for ZVOLs. Now you have 6.09 TB occupied, and 5.96 more are available in total on datasets:
hdd1/ESXi 4.06T 4.39T 389G -
hdd1/ESXi1 1.02T 1.57T 158G -
(second column -- available space). Which in total gives us 12.05 TB. Plus 728 GB available on the core dataset. In total, it turns out ~ 12.8 TB. Plus or minus, taking into account metadata, here it is your volume, no?