The present invention provides a reliable and high-speed data transfer method that achieves a high 
transfer efficiency and a high application 
processing efficiency concurrently and a disk 
control unit (
disk controller) using such a method. In reliable data transfer in which, when data is transferred from an initiator to a target, the data received by the target is checked for validity by using an 
error check code attached to the data, a 
transfer status indicating whether the data is valid is returned from the target to the initiator, and, if a 
transfer error occurring during the data transfer is detected by the 
transfer status, the initiator retries to transfer the data to the target, a data transfer method for logical records that are units of data transfer between the initiator and the target is disclosed. This method is characterized in that: when each logical 
record transferred by a transfer request issued by the initiator arrives correctly on the target, the target posts a 
completion status corresponding to the transfer request for the logical 
record to a completion 
queue existing in the target; a plurality of logical records in a block are batch transferred; the initiator confirms the 
transfer status at every batch transfer; and, for each logical 
record that meets a predetermined batch transfer condition, the target posts a 
completion status corresponding to the transfer request for the logical record to the completion 
queue existing in the target upon correct reception of the logical record.