Strange problems with my zvol

[lohmag]

Hello everyone.
I have zvol which is iscsi target. Today my Windows 2008 initiator hang up after reboot all iscsi volumes doesn't appear. What i discover
Freenas iscsi demon can't start -

Code:

Mar 24 11:00:28 freenas istgt[6799]: istgt version 0.5 (20121028)
Mar 24 11:00:28 freenas istgt[6799]: normal mode
Mar 24 11:00:28 freenas istgt[6799]: using kqueue
Mar 24 11:00:28 freenas istgt[6799]: using host atomic
Mar 24 11:00:28 freenas istgt[6799]: istgt_lu_disk.c: 367:istgt_lu_disk_allocate_raw: ***ERROR*** lu_disk_write() failed
Mar 24 11:00:28 freenas istgt[6799]: istgt_lu_disk.c: 650:istgt_lu_disk_init: ***ERROR*** LU2: LUN0: allocate error
Mar 24 11:00:28 freenas istgt[6799]: istgt_lu.c:2091:istgt_lu_init_unit: ***ERROR*** LU2: lu_disk_init() failed
Mar 24 11:00:28 freenas istgt[6799]: istgt_lu.c:2166:istgt_lu_init: ***ERROR*** LU2: lu_init_unit() failed
Mar 24 11:00:28 freenas istgt[6799]: istgt.c:2799:main: ***ERROR*** istgt_lu_init() failed
Mar 24 11:00:29 freenas root: /etc/local/rc.d/istgt: WARNING: failed to start istgt

After some googling i find out thet it could be zvol low space problem and it is

Code:

zfs get all VOL1/VOL1
NAME      PROPERTY              VALUE                  SOURCE
VOL1/VOL1  type                  volume                -
VOL1/VOL1  creation              Wed Dec  4 14:36 2013  -
VOL1/VOL1  used                  20.4T                  -
VOL1/VOL1  available            0                        -
VOL1/VOL1  referenced            18.2T                  -
VOL1/VOL1  compressratio        1.20x                  -
VOL1/VOL1  reservation          none                  default
VOL1/VOL1  volsize              18.5T                  local
VOL1/VOL1  volblocksize          16K                    -
VOL1/VOL1  checksum              on                    default
VOL1/VOL1  compression          lz4                    inherited from VOL1
VOL1/VOL1  readonly              off                    default
VOL1/VOL1  copies                1                      default
VOL1/VOL1  refreservation        none                  default
VOL1/VOL1  primarycache          all                    default
VOL1/VOL1  secondarycache        all                    default
VOL1/VOL1  usedbysnapshots      2.20T                  -
VOL1/VOL1  usedbydataset        18.2T                  -
VOL1/VOL1  usedbychildren        0                      -
VOL1/VOL1  usedbyrefreservation  0                      -
VOL1/VOL1  logbias              latency                default
VOL1/VOL1  dedup                off                    inherited from VOL1
VOL1/VOL1  mlslabel                                    -
VOL1/VOL1  sync                  standard              default
VOL1/VOL1  refcompressratio      1.15x                  -
VOL1/VOL1  written              84.4G                  -
VOL1/VOL1  logicalused          19.1T                  -
VOL1/VOL1  logicalreferenced    16.7T                  -

I deleted some snapshots to make available space

Code:

 zfs get all VOL1/VOL1
NAME      PROPERTY              VALUE                  SOURCE
VOL1/VOL1  type                  volume                -
VOL1/VOL1  creation              Wed Dec  4 14:36 2013  -
VOL1/VOL1  used                  18.2T                  -
VOL1/VOL1  available            255G                  -
VOL1/VOL1  referenced            18.2T                  -
VOL1/VOL1  compressratio        1.15x                  -
VOL1/VOL1  reservation          none                  default
VOL1/VOL1  volsize              18.5T                  local
VOL1/VOL1  volblocksize          16K                    -
VOL1/VOL1  checksum              on                    default
VOL1/VOL1  compression          lz4                    inherited from VOL1
VOL1/VOL1  readonly              off                    default
VOL1/VOL1  copies                1                      default
VOL1/VOL1  refreservation        none                  default
VOL1/VOL1  primarycache          all                    default
VOL1/VOL1  secondarycache        all                    default
VOL1/VOL1  usedbysnapshots      0                      -
VOL1/VOL1  usedbydataset        18.2T                  -
VOL1/VOL1  usedbychildren        0                      -
VOL1/VOL1  usedbyrefreservation  0                      -
VOL1/VOL1  logbias              latency                default
VOL1/VOL1  dedup                off                    inherited from VOL1
VOL1/VOL1  mlslabel                                    -
VOL1/VOL1  sync                  standard              default
VOL1/VOL1  refcompressratio      1.15x                  -
VOL1/VOL1  written              18.2T                  -
VOL1/VOL1  logicalused          16.7T                  -
VOL1/VOL1  logicalreferenced    16.7T                  -

Code:

 zfs get refquota,reservation,refreservation
NAME          PROPERTY        VALUE      SOURCE
VOL1          refquota        none      local
VOL1          reservation    none      default
VOL1          refreservation  none      local
VOL1/.samba4  refquota        none      default
VOL1/.samba4  reservation    none      default
VOL1/.samba4  refreservation  none      default
VOL1/VOL1    refquota        -          -
VOL1/VOL1    reservation    none      default
VOL1/VOL1    refreservation  none      default
VOL2          refquota        none      local
VOL2          reservation    none      default
VOL2          refreservation  none      local
VOL2/VOL2    refquota        -          -
VOL2/VOL2    reservation    none      default
VOL2/VOL2    refreservation  none      local

But the thing is - Windows show me a lot of free space
http://clip2net.com/s/74MEyk
I'm afraid that after day or two space is runs out and there is no snapshots to delete!