In SCSI protocol, the client which requests data is known as the initiator. The initiator typically resides on the host server that is accessing the storage. Initiators can also reside in storage virtualization boxes which can act as both initiators and targets.
The SCSI initiator can reside in software or in a hardware adapter card. SCSI protocol provides commands that allow initiators to reserve LUNs and prevent them from being accessed by other initiators. SCSI initiators communicate with SCSI targets using SCSI block level protocol. The block level protocol data is transported via other transport protocols such as parallel SCSI, Fiber Channel, Serial SCSI or Infiniband.