On 07/07/2011 04:37 PM, SR wrote: > Hi, > > If I have following negotiated parameters for iscsi read command then > are following explained scenarios possible (I wasn't sure about > scenario-1) ? > > MaxBurstLength = 128K > FirstBurstLength = 32K
For reads FirstBurstLength does not come into play. It is just for writes and immediate data and initial r2t handling. > MaxRecvDataSegmentLength = 8K > SCSI (read) command PDU specifies total data length = 25K > > Which scenario out of following two should be considered is correct > operation? Is scenario-1 possible? > What are the main factors taken into account before chopping SCSI data > into iSCSI PDU? > > Scenario-1: > > iSCSI Data-In PDUs: > > PDU1 with data length=4K > PDU2 with data length=4K > PDU3 with data length=4K > PDU4 with data length=4K > PDU5 with data length=4K > PDU6 with data length=4K > PDU7 with data length=1K I think the iscsi RFC just says that the target cannot send more than MaxRecvDataSegmentLength bytes, so it is valid for it to send PDUs with only 4K. > > Scenario-2: > > iSCSI Data-In PDUs: > > PDU1 with data length=8K > PDU2 with data length=8K > PDU3 with data length=8K > PDU4 with data length=1K I think this is more common. > > Can you point me to the code where this decision is made about > chopping SCSI data into iSCSI PDU. > The initiator does not do the chopping for READs. The target does this. We just read in whatever the target sends us. For WRITEs there is iscsi_prep_scsi_cmd_pdu and iscsi_prep_data_out_pdu/iscsi_tcp_r2t_rsp. -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to email@example.com. To unsubscribe from this group, send email to open-iscsi+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/open-iscsi?hl=en.