switches, each ESX server must be configured with a minimum of two VMkernel ports in the same VSwitch. This VSwitch is configured with a minimum of two network adapters. Each of these VMkernel ports supports IP traffic on a different subnet. Because the two VMkernel ports are in the same VSwitch they can share the physical network adapters in that VSwitch. EXPLAING ESX SERVER ADAPTER FAILOVER BEHAVIOR In case of ESX server adapter failure (due to a cable pull or NIC failure), traffic originally running over the failed adapter is rerouted and continues via the second adapter but on the same subnet where it originated. Both subnets are now active on the surviving physical adapter. Traffic returns to the original adapter when service to the adapter is restored REVIEWING LINK AGGREGATION WITHIN ESX SERVER ESX server supports static Link Aggregation. Link Aggregation provides the means to channel multiple network ports. The channeling of ports provides a means to distribute traffic based on source and destination and to increate link redundancy for higher availability. In this document any reference to Etherchannel in the terms of configuring an ESX server is actually referring to a static etherchannel. ESX server does not support the use of LACP 802.3ad.. SWITCH FAILURE Traffic originally running to the failed switch is rerouted and continues via the other available adapter, through the surviving switch, to the NetApp storage controller. Traffic returns to the original adapter when the failed switch is repaired or replaced. CONNECTING TO DATASTORES With Ethernet based storage networking protocols VMware datastores are mounted by IP addresses. Both iSCSI & NFS access datastores by a single IP address. With both iSCSI and NFS datastores multiple datastores are required to make use of multiple IP paths simultaneously on each ESX/ESXi host. Using NFS to connect to the same volume multiple times from a single ESX/ESXi host should be avoided, as ESX/ESXi and vCenter will consider these connections to be different datastores. Note with iSCSI this design is represented as multiple IP paths to a single SCSI target, only one IP path is active per datastore, however each ESX/ESXi host may use a different active IP path. Regarding NFS datastores each datastore should be connected only once from each ESX/ESXi server, and using the same netapp target IP address on each ESX/ESXi server.
43 Figure 26) ESX vSwitch1 normal mode operation. Figure 27) ESX vSwitch1 failover mode operation. SCALABILITY OF ESX SERVER NETWORK CONNECTIONS Although the configuration shown in the figure above uses two network adapters in each ESX Server, it could be scaled up to use additional adapters, with another VMkernel port, subnet, and IP address added for each additional adapter. Another option would be to add a third adapter and configure it as an N+1 failover adapter. By not adding more VMkernel ports or IP addresses, the third adapter could be configured as the first standby port for both VMkernel ports. In this configuration, if one of the primary physical adapters fails, the third adapter assumes the failed adapter’s traffic, providing failover capability without reducing the total amount of potential network bandwidth during a failure.