Trace System of iSCSI Storage Access

In this paper, an IP-SAN access trace method is proposed and its implementation is presented. IP-SAN and iSCSI are expected to remedy problems of fibre channel (FC)-based SAN. Because servers and storage cooperatively work with communications through TCP/IP layer in IP-SAN system, an integrated analysis of both sides is considered to be significant for achieving better performance. Our proposed system can precisely point out the cause of performance degradation when IP-SAN is used for a remote storage access. In the experiment of parallel iSCSI access in a long-delayed network, the total performance is limited by a parameter in an implementation of the SCSI layer in the iSCSI protocol stack. Based on the result obtained with our IP-SAN access trace system, the parameter in the layer is modified. As a result, four times performance improvement is achieved compared with the default value case. Thus it is effective to monitor all the layers in the iSCSI protocol stack and execute an integrated analysis, using our system.