vsphere-esxi-vcenter-server-55-storage-guide

vSphere StorageArray-Based Failover with iSCSISome iSCSI storage systems manage path use of their ports automatically and transparently to ESXi.When using one of these storage systems, your host does not see multiple ports on the storage and cannotchoose the storage port it connects to. These systems have a single virtual port address that your host uses toinitially communicate. During this initial communication, the storage system can redirect the host tocommunicate with another port on the storage system. The iSCSI initiators in the host obey this reconnectionrequest and connect with a different port on the system. The storage system uses this technique to spreadthe load across available ports.If the ESXi host loses connection to one of these ports, it automatically attempts to reconnect with the virtualport of the storage system, and should be redirected to an active, usable port. This reconnection andredirection happens quickly and generally does not disrupt running virtual machines. These storagesystems can also request that iSCSI initiators reconnect to the system, to change which storage port they areconnected to. This allows the most effective use of the multiple ports.The Port Redirection illustration shows an example of port redirection. The host attempts to connect to the10.0.0.1 virtual port. The storage system redirects this request to 10.0.0.2. The host connects with 10.0.0.2 anduses this port for I/O communication.NOTE The storage system does not always redirect connections. The port at 10.0.0.1 could be used for traffic,also.Figure 23‐3. Port Redirection“Connect to storage at 10.0.0.1”Host 1“Reconnect to 10.0.0.2”10.0.0.110.0.0.2storageHost 2iSCSI storage traffic10.0.0.110.0.0.2storageIf the port on the storage system that is acting as the virtual port becomes unavailable, the storage systemreassigns the address of the virtual port to another port on the system. Port Reassignment shows an exampleof this type of port reassignment. In this case, the virtual port 10.0.0.1 becomes unavailable and the storagesystem reassigns the virtual port IP address to a different port. The second port responds to both addresses.218 VMware, Inc.