FAQ / How do I configure COMSTAR iSCSI targets for fail over?

When adding a shared volume to a cluster which will have zvols created as backing storage for iSCSI targets, it is vital all client iSCSI initiators, irrespective of operating system, are configured to access those targets using the shared logical hostname specified when the volume service was created, rather than a real hostname associated with one of the appliances.

It is important to note that the cluster handles all aspects of the shared logical hostname configuration; therefore you should never attempt to configure the shared logical hostname manually. Furthermore, unless the shared volume service is running, the shared logical hostname should not be present on the network (this can be verified with the ICMP ping command).

To configure iSCSI targets on the appliance where the volume service is currently running, select Data Management->SCSI Target in NMV, followed by Create from the Zvols pane to create a virtual block device, in this example zvol01 with a size of 200MB from the shared volume vol01. The newly created zvol is automatically migrated to the other appliance on failover, therefore it does not need to be duplicated manually on other nodes in the cluster.

zvol

Once the zvol has been created, select Target Portal Groups from the iSCSI pane to define a target portal group (tpg01); it is vital the IPv4 portal address is the shared logical hostname (192.168.33.135) specified when the volume service was created, not a real hostname associated with one of the appliances. The newly created target portal group is automatically replicated to the other appliance, therefore it does not to need to be duplicated manually.

target portal group

Once the target portal group has been defined, select Targets from the iSCSI pane to create an iSCSI target and add the target portal group defined in the previous step to limit zvol visibility from client initiators to the target portal group. Again, the newly created iSCSI target is automatically replicated to the other appliance, therefore it does not to need to be duplicated manually.

target

The newly created iSCSI target (iqn.1986-03.com.sun:02:9d5ba857-c064-e538-9e5a-eac99840dd0d) is now displayed in the Targets page:

target 2

Once the iSCSI target has been created with the target portal group, select Mappings from the SCSI Target pane to create a LUN mapping to the zvol to be used as backing storage for the iSCSI target. The newly created LUN mapping is automatically migrated to the other appliance on failover, therefore it does not need to be duplicated manually.

mappings

Finally, on the client regardless of operating system, it is vital the iSCSI initiator is configured to use both the IQN (iqn.1986-03.com.sun:02:9d5ba857-c064-e538-9e5a-eac99840dd0d) of the iSCSI target created and the shared logical hostname (192.168.33.135) associated with both the volume service and target portal group (tpg01) to access the zvol (zvol01) via iSCSI.

For example, on OpenSolaris:

client

Posted in: NexentaStor