6.5.1

Table Of Contents
Array-Based Failover with iSCSI
Some 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
cannot choose the storage port it connects to. These systems have a single virtual port address that your
host uses to initially communicate. During this initial communication, the storage system can redirect the
host to communicate with another port on the storage system. The iSCSI initiators in the host obey this
reconnection request and connect with a different port on the system. The storage system uses this
technique to spread the load across available ports.
If the ESXi host loses connection to one of these ports, it automatically attempts to reconnect with the
virtual port of the storage system, and should be redirected to an active, usable port. This reconnection
and redirection happens quickly and generally does not disrupt running virtual machines. These storage
systems can also request that iSCSI initiators reconnect to the system, to change which storage port they
are connected 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
the 10.0.0.1 virtual port. The storage system redirects this request to 10.0.0.2. The host connects with
10.0.0.2 and uses 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 183. Port Redirection
storage
10.0.0.1
10.0.0.2
Host 1
“Connect to storage at 10.0.0.1”
“Reconnect to 10.0.0.2”
storage
10.0.0.1
10.0.0.2
Host 2
iSCSI storage traffic
If the port on the storage system that is acting as the virtual port becomes unavailable, the storage
system reassigns the address of the virtual port to another port on the system. Port Reassignment shows
an example of this type of port reassignment. In this case, the virtual port 10.0.0.1 becomes unavailable
and the storage system reassigns the virtual port IP address to a different port. The second port responds
to both addresses.
vSphere Storage
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