6.0.1

Table Of Contents
Figure 172. Host-Based Path Failover
IP network
hardware
iSCSI
host 1
SP
iSCSI storage
HBA2 HBA1
software
iSCSI
host 2
NIC2 NIC1
software
adapter
Failover with Hardware iSCSI
With hardware iSCSI, the host typically has two or more hardware iSCSI adapters available, from which the
storage system can be reached using one or more switches. Alternatively, the setup might include one
adapter and two storage processors so that the adapter can use a dierent path to reach the storage system.
On the Host-Based Path Failover illustration, Host1 has two hardware iSCSI adapters, HBA1 and HBA2, that
provide two physical paths to the storage system. Multipathing plug-ins on your host, whether the
VMkernel NMP or any third-party MPPs, have access to the paths by default and can monitor health of each
physical path. If, for example, HBA1 or the link between HBA1 and the network fails, the multipathing
plug-ins can switch the path over to HBA2.
Failover with Software iSCSI
With software iSCSI, as shown on Host 2 of the Host-Based Path Failover illustration, you can use multiple
NICs that provide failover and load balancing capabilities for iSCSI connections between your host and
storage systems.
For this setup, because multipathing plug-ins do not have direct access to physical NICs on your host, you
rst need to connect each physical NIC to a separate VMkernel port. You then associate all VMkernel ports
with the software iSCSI initiator using a port binding technique. As a result, each VMkernel port connected
to a separate NIC becomes a dierent path that the iSCSI storage stack and its storage-aware multipathing
plug-ins can use.
For information on how to congure multipathing for software iSCSI, see “Seing Up iSCSI Network,” on
page 88.
Chapter 17 Understanding Multipathing and Failover
VMware, Inc. 185