iSCSI Storage

iSCSI is a protocol that enables clients, called initiators, to send SCSI commands to SCSI storage devices, called targets, on remote servers. It is a Storage Area Network (SAN) protocol that enables the consolidation of storage into data-center storage arrays, while providing hosts with the illusion of locally attached disks. The use of iSCSI does not require special-purpose cabling. Instead, communication is run over long distances by using the existing network infrastructure.

Observe the following guidelines for configuring iSCSI storage in an Open HA Cluster configuration:

• COMSTAR – Only COMSTAR based iSCSI target implementations are supported in an Open HA Cluster 2009.06 configuration.

• iSCSI target location – A disk that is exported as an iSCSI target must be a local disk that is directly attached to the cluster node that hosts the iSCSI target. You cannot use a disk as an iSCSI target if it is hosted by multiple nodes or if it is not directly attached to the cluster node.

• Topology – Configure the hardware connections as shown in the following diagram. This diagram shows a two-node Open HA Cluster 2009.06 configuration that uses COMSTAR and a failover ZFS storage pool to provide high availability. The arrows indicate iSCSI connections. One or more connections provide a path from each node to the same disk on Node 1. In the cluster DID namespace, this becomes a single DID device, with paths from both nodes. Similarly, one or more connections provide a path from each node to the same disk on Node 2. This creates a second DID device. The mirroring of these two DID devices by using a ZFS storage pool creates a failover ZFS file system in the Open HA Cluster configuration.

Figure 1–1 Cluster Topology Using Unshared COMSTAR Storage