Network configuration for iSCSI

iSCSI makes it possible to construct an IP-SAN by connecting many hosts and storage systems at a low cost. However, iSCSI greatly increases the I/O workload of the network and the storage system. When using iSCSI, it is very important that you configure the network so that the workload among the network, port, controller, and drive is properly distributed.

Even though the LAN switches and NICs are the same, there are some important differences when you use iSCSI, particularly regarding the LAN connection. You need to pay particular attention to the following:

• iSCSI consumes almost all of the available Ethernet bandwidth, unlike a conventional LAN connection. This can significantly degrade the performance of both the iSCSI traffic and the LAN. Therefore, it is very important that you separate the iSCSI IP-SAN and the office LAN.

• Host I/O load will affect the iSCSI response time. In general, the greater the I/O traffic is, the lower the iSCSI performance.

• You need to have a failover path between host and iSCSI, so that you can update the firmware without stopping the system.

The following figure shows LU paths configuration in a Fibre Channel environment. The figure shows the iSCSI target 00 associated with three logical volumes (00:00:00, 00:00:01, and 00:00:02). LU paths are defined between the two hosts in the iSCSI target 00 and the three logical volumes.

You can define paths between a single server host and multiple LUs. The figure shows that each of the two hosts in the iSCSI target 00 can access the three LUs.

You can also define paths between multiple server hosts and a single LU. The figure shows that the LU identified by the LDKC:CU:LDEV number 00:00:00 is accessible from the two hosts that belong to the iSCSI target 00.