User guide
Technical white paper | HP Enterprise Virtual Array Storage and VMware vSphere 4.x and 5.x configuration best practices
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Figure 12 below, shows the iSCSI target to GbE port connections from a single 1GbE iSCSI Module perspective on one array
controller.
Figure 12. Logical view of iSCSI target connection to GbE ports – Single controller view.
From an ESX host perspective, ESX has the proper NIC redundancy and will detect its maximum of eight paths per LUN. If NIC
1 (port 1 in Figure 12) failed, I/O would be failed over to an available iSCSI target through NIC 2 (port 2 in Figure 13).
However, from an array perspective, all paths to LUNs are built through iSCSI targets on the same controller. If this
controller was to fail or reboot, the host would lose all access to storage because the maximum number of paths was
exhausted through access to controller 1 and no paths to LUNs were built using the paths through controller 2.
When using an EVA with a 1GbE iSCSI Module option and all GbE ports must be attached to the iSCSI SAN, it is recommended
to use Static discovery on the ESX side and manually select which iSCSI targets will be exposed to ESX for LUN access.
Alternatively, a more adequate high availability configuration is shown in Figure 14 below where only two GbE ports per
controller are attached to the iSCSI SAN and two NICs are used in the host.
Figure 13. Logical view of iSCSI target connection to GbE ports – Dual controller view.
In this configuration, iSCSI Dynamic discovery can be used to enable ease of deployment while ensuring proper high
availability.
In an EVA with a 1GbE iSCSI Module option configuration, high availability via redundant paths is dependent on the following
factors:
• The number of NIC adapters in the host accessing the iSCSI SAN
• The number of iSCSI targets exposed to the iSCSI SAN
• The iSCSI discovery type used
Table 2 below provides guidance to select the right number of paths at the host and at the array to maintain proper high
availability in a 1GbE iSCSI Module configuration with two distinct SANs as shown in Figure 10.