I was refering to the online help when creating FC Target, so I selected 4096

Blocksize
This option is available when creating a Fibre Channel volume (FC). Blocksize indicates the nominal size, expressed in bytes, of a block of data. Possible values:

512 bytes
1024 bytes
2048 bytes
4096 bytes (default)

Blocksize has an influence on performance and space management. The greater value the better performance, but data might take up more space. This option is unavailable when modifying an FC volume and for FC snapshots.