order to achieve path high availability. THE MULTI-MODE DESIGN The multi-mode design requires each storage controller to have at least four physical network connections (depicted). The connections are divided into two multimode (active/active) VIFs with IP load balancing enabled, one VIF connected to each of the two switches. These two VIFs are then combined into one single mode (active/passive) VIF. NetApp refers to this configuration as a second-level VIF. This option also requires multiple IP addresses on the storage appliance. Multiple IP addresses can be assigned to the single-mode VIF by using IP address aliases or by using VLAN tagging. ADVANTAGES OF USING MULTI MODE VIFS ± Storage controller connection load balancing is automatically managed by the Etherchannel IP load balancing policy. ± Data I/O to a single IP is aggregated over multiple links DISADVANTAGES OF USING MULTI MODE VIFS Some switch side configuration is required. Some storage traffic will cross the uplink between the two switches. Figure 30) Storage side multimode VIFs.
47 THE SINGLE-MODE DESIGN The single-mode design requires each pair of network links to be configured as a single mode (active/passive) VIF. Each VIF has a connection to both switches and has a single IP address assigned to it, providing two IP addresses on each controller. The vif favor command is used to force each VIF to use the appropriate switch for its active interface. This option is preferred due to its simplicity and the lack of any special configuration on the network switches. ADVANTAGES OF USING SINGLE MODE VIFS Simplicity - No switch side configuration is required. DISADVANTAGES OF USING SINGLE MODE VIFS Data I/O to a single IP is not aggregated over multiple links without adding more links. Figure 31) Storage side single-mode VIFs.