Usage: iscsi_readcapacity16 [OPTION...] <iscsi-url>
  -i, --initiator-name=iqn-name     Initiatorname to use
  -o, --offset                      Byte offset into the target from which to start discarding. The provided value must be aligned to the target sector size. The default value is zero.
  -l, --length                      The number of bytes to discard (counting from the starting point). The provided value must be aligned to the target sector size. If the specified value extends past the end of the device, iscsi-discard will stop at the device size boundary. The default value extends to the end of the device.
  -z, --zeroout                     Zero-fill rather than discard.
  -d, --debug=integer               debug level (0=disabled)

Help options:
  -?, --help                        Show this help message

iSCSI URL format : "iscsi://[<username>[%<password>]@]<host>[:<port>]/<target-iqn>/<lun>"

<host> is either of:
  "hostname"       iscsi.example
  "ipv4-address"   10.1.1.27
  "ipv6-address"   [fce0::1]